Allow users to specify their preferred configuration directory by using
the top level flag (a.k.a 'global flag') --config-dir. This also
introduces the design of baking top level flags into the executor.
Add Enbas code. So far Enbas can:
- Allow the user to register the application and log into GTS on their
behalf. The scope is limited to read for now.
- Show instance details.
- Show local and remote accounts.
