Fix sessions.py header
Add CLI/API for passing sudo parameter
sessions.py: Add call to createSessionWithTimeouts
Fix empty string bugs in SessionManagerImpl

Probably since the move to Ice, null strings in the
Principal object have been converted to empty strings
which have failed the various tests for setting defaults.
Record 'omero.sudo' in session file
Fix unit test test_sess.py
Add test_login.py for CLI
Improve `bin/omero sessions help`
Remove unused 'def sudo'
Improve login help incl. `-sudo`

Previously, `bin/omero sessions login -h` and
`bin/omero login -h` differed in their help
text. Now they match and the most basic uses
are (briefly) listed.
Fix flake8 warnings
Merge pull request #2272 from joshmoore/rebased/develop/login-as-cli

Login as cli (rebased onto develop)