Use monkeypatch for bin/omero config envvar unittests
Add subcommands help tests to test_prefs.py
Add failing tests for bin/omero config drop and set subcommands
Add first implementation of remove and append subcommand with unit test
Fix remove with only one item and add error handling in append/remove
Add unit tests for failing append/remove calls
Optimize duplicate line
Only support file input for omero config set subcommand
Review failing append/remove unit tests
Fix omero config subcommands description by using parser.add()
Add append and remove to the subcommand list in test_prefs.py
Fix description and help of various omero config commands/arguments
Expand "standard in" to "standard input"
Use JSON to read/write config lists
Also load passed values as JSON in append/remove commands
Defaults config value to empty list after last item removal

- Update corresponding unit tests
- Add test for removal of multi-defined item
Load default when appending to/removing from an unset omero.web property
Fix variable
Add tests for omero.web property default value retrieval
Monkeypatch ConfigXml so that config.xml is not being read