Add method to retrieve given annotation linked to object.

Method useful to retrieve annotation like modulo annotation
added at import time.
Fix class cast exception.
Fix query to load annotations.
Using OME.well_selection_changed() to work with jshint PR545
Webadmin: system group 'X' hidden in chosen. See PR 565
Fix removal of Tags/Files from Wells. See #10004
Add tests for modulo retrieval.
Add modulo namespace to constant.
Add test to create XML annotation.
Review existing tests.
Add modulo ns to pojos and add test using modulo ns.
Fix documentation.
merge dev_4_4 --exclude conflict needs-fixes broken: PR 482 (int(request.REQUEST.get('index', 0) all in try/except. See #9918)
merge dev_4_4 --exclude conflict needs-fixes broken: PR 536 (Insight import location)
merge dev_4_4 --exclude conflict needs-fixes broken: PR 538 (OMERO.tables ArrayColumns #5632)
merge dev_4_4 --exclude conflict needs-fixes broken: PR 539 (Fix initialisation of username on Windows)
merge dev_4_4 --exclude conflict needs-fixes broken: PR 545 (Jshint compliance 9927)
merge dev_4_4 --exclude conflict needs-fixes broken: PR 552 (Channel naming 100022)
merge dev_4_4 --exclude conflict needs-fixes broken: PR 558 (Plugin dependencies)
merge dev_4_4 --exclude conflict needs-fixes broken: PR 565 (Web bugs 18th dec)