Search for OFs in all user groups.

The addition of omero.group = -1 into the method call context
forces the query to execute across all groups where the
user is a member.
Add test case.
Extended search for all object types.

This also handles downloading of images and
file annotations. The changes preserve the
omero.client.uuid string in the context.
Initial version of Python integration tests.
Fix flake8 error (E303).
Refactor use of implicit to getContext()

Added helper method for any omero.client user.
Eventually, kwargs could be present for all of
the uses ("omero.user", "omero.uuid", etc.)
Remove semicolons from code.
Merge pull request #2398 from bpindelski/rebased/develop/12146_all_groups

CLI download looks for resources in all user groups (fix #12146). (rebased onto develop)