Fix for non-existing Pixels directory in bin/omero admin cleanse

OME-DCO-1.1-Signed-off-by: Sebastien Besson <seb.besson@gmail.com> (github: sbesson)
Do not restrict existence check to Pixels directory in cleanse command

OME-DCO-1.1-Signed-off-by: Sebastien Besson <seb.besson@gmail.com> (github: sbesson)
Fix passing testImportMultiGroup integration test and remove xfail

- Modify get_object to pass {'omero.group': -1}
- Set arguments rather than session key to allow -g
Refactor set_conn_args() and move '--sudo' arguments to the tests
Pass omero.group to omero.sys.Principal when creating sudo session
Remove xfail mark from testImportAsRootMultiGroup
Rename test_login.py as test_sessions.py and remove duplicate register
Add eventContext test to testLoginAsRoot
Add eventContext test to testLoginAsGroupAdmin
Remove unused capsys fixture
Add integration tests for login in multi-group with/without sudo
Refactor connection arguments settings for Login tests
Store the new event context during session group for testing
Add integration test for session group command
merge develop -D org: PR 2127 (Working view to email announcements to selected users, groups, email addresses and/or all users)
merge develop -D org: PR 2336 (New tagging dialog)
merge develop -D org: PR 2362 (Remove .jy from script names)
merge develop -D org: PR 2391 (Imagej omero (rebased onto develop))
merge develop -D org: PR 2411 (Update develop submodules)
merge develop -D org: PR 2435 (cpp: RTypesI: use static locals in place of duplicated globals)