add a "postFilter" operation

It takes a documentList in input, and return a filtered documentList.
Filter possibilities would be on document type, lifecycle and properties (JPE expression).

Use cases are : filter the content of the worklist, filter the content of document selection, of a getChildren... Objective of filtering is to be sure that the following operations won't fail (ex : play life cycle transition, which breaks if the document has not the good state, etc....) and will work on "compatible" documents