Allow cached settings to be cleared via CLI

[bruno-f-cruz]

As of 2.9, settings are now stored per environment. It may be useful to allow an extra CLI command that "clears" all the files inside "settings". This would allow users to automatically clear settings in cases where branches are switched frequently and mismatches in layout files are expected.
Note that while as of 2.9 bonsai will try to recover from corrupted layouts, I have seen a few edge cases, especially related to complex nested TableLayout structures.