optimise list workflow instance in dashboard

Added the method boolean selectThisItem(WMWorkItemInstance ) to the WorkflowDocumentSecurityPolicy interface. It should tell either this work instance should be selected for display in the dashboard. A default method in AbstractWorkflowSecurityPolicy returns always true. Added method ResultSlice<WMWorkItemInstance> getWorkItemsFor( List<WMParticipant> participants, String state, int firstResult, int maxResults) to get paginated workinstances fetch every call to WAPI.startProcess should have WorkflowConstants.WORKFLOW_CREATOR set to currentUser.getName() to get the getWorkItemsFor methods to work correctly. This is already the case in nuxeo by default but might not be the case in custom workflows A workflow should always have a variable named "author" (WorkflowConstants.WORKFLOW_CREATOR)