Improve error message on missing field in webdriver tests

org.openqa.selenium.TimeoutException: Timed out after 30 seconds waiting for org.nuxeo.functionaltests.AbstractTest$1@687e4c93
Build info: version: '2.39.0', revision: '14fa800511cc5d66d426e08b0b2ab926c7ed7398', time: '2013-12-16 13:18:38'
System info: host: 'ip-10-124-4-247', ip: '10.124.4.247', os.name: 'Linux', os.arch: 'amd64', os.version: '3.13.0-45-generic', java.version: '1.8.0_40'
Driver info: driver.version: unknown
	at org.openqa.selenium.support.ui.FluentWait.timeoutException(FluentWait.java:259)
	at org.openqa.selenium.support.ui.FluentWait.until(FluentWait.java:228)
	at org.nuxeo.functionaltests.AbstractTest.fillElement(AbstractTest.java:674)
	at org.nuxeo.functionaltests.AbstractTest.asPage(AbstractTest.java:632)
	at org.nuxeo.functionaltests.pages.AbstractPage.asPage(AbstractPage.java:67)
	at org.nuxeo.functionaltests.pages.DocumentBasePage.getWorkspacesContentTab(DocumentBasePage.java:273)
	at org.nuxeo.functionaltests.AbstractTest.createWorkspace(AbstractTest.java:837)
	at org.nuxeo.functionaltests.AbstractTest.initRepository(AbstractTest.java:808)
	at org.nuxeo.ftest.cap.ITNoteDocumentTest.testCreateAndEditNote(ITNoteDocumentTest.java:122)

org.openqa.selenium.TimeoutException: not loaded: createNewWorkspaceLink
Build info: version: '2.39.0', revision: '14fa800511cc5d66d426e08b0b2ab926c7ed7398', time: '2013-12-16 13:18:38'
System info: host: 'nocode', ip: '127.0.1.1', os.name: 'Linux', os.arch: 'amd64', os.version: '3.19.0-28-generic', java.version: '1.8.0_60'
Driver info: driver.version: unknown
	at org.nuxeo.functionaltests.AbstractTest.fillElement(AbstractTest.java:691)
	at org.nuxeo.functionaltests.AbstractTest.asPage(AbstractTest.java:636)
	at org.nuxeo.functionaltests.pages.AbstractPage.asPage(AbstractPage.java:67)
	at org.nuxeo.functionaltests.pages.DocumentBasePage.getWorkspacesContentTab(DocumentBasePage.java:273)
	at org.nuxeo.functionaltests.AbstractTest.createWorkspace(AbstractTest.java:844)
	at org.nuxeo.functionaltests.AbstractTest.initRepository(AbstractTest.java:815)
	at org.nuxeo.ftest.cap.ITNoteDocumentTest.testCreateComplexNote(ITNoteDocumentTest.java:79)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.nuxeo.functionaltests.LogTestWatchman$1.evaluate(LogTestWatchman.java:94)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: org.openqa.selenium.TimeoutException: Timed out after 5 seconds waiting for org.nuxeo.functionaltests.AbstractTest$1@46d59067
Build info: version: '2.39.0', revision: '14fa800511cc5d66d426e08b0b2ab926c7ed7398', time: '2013-12-16 13:18:38'
System info: host: 'nocode', ip: '127.0.1.1', os.name: 'Linux', os.arch: 'amd64', os.version: '3.19.0-28-generic', java.version: '1.8.0_60'
Driver info: driver.version: unknown
	at org.openqa.selenium.support.ui.FluentWait.timeoutException(FluentWait.java:259)
	at org.openqa.selenium.support.ui.FluentWait.until(FluentWait.java:228)
	at org.nuxeo.functionaltests.AbstractTest.fillElement(AbstractTest.java:679)
	... 34 more