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
OmeroCpp: Correct stringstream usage in cmdcallbacktest
OmeroCpp: Correct use of rbool
customizing 'Orphaned images' container
add comment to settings.py
fixing custom template tag for retrieving settings

to display empty string instead of None
updating year in copyrights & spelling mistake
introducing hidden settings
adding default settings in process_custom_settings()
build: Use safe javac macro for test compilation