Fix upgrade and validation of projects

Upgrade is currently failing when some given project is not found:

Caused by: org.nuxeo.studio.client.model.NoSuchProjectException: No such project IRD
at org.nuxeo.studio.core.impl.NuxeoSession.getDocument(NuxeoSession.java:168)
at org.nuxeo.studio.core.impl.NuxeoSession.getProjectSettings(NuxeoSession.java:155)
at org.nuxeo.studio.core.impl.AbstractSession.getProject(AbstractSession.java:98)
at org.nuxeo.studio.core.upgrade.UpgradeContext.<init>(UpgradeContext.java:62)
at org.nuxeo.studio.core.upgrade.UpgradeContext.<init>(UpgradeContext.java:55)
at org.nuxeo.studio.core.upgrade.PersistenceUpgradeService.upgradeAll(PersistenceUpgradeService.java:121)
at org.nuxeo.studio.web.StudioAdmin.doUpgrade(StudioAdmin.java:97)

+ some NPEs happen in the document and search upgrade

+ upgraded files are not written correctly to the disk

+ revert does not put back files backed up...