This change allows users to init a new airship config file or
specify an existing one if it hasn't been found in the default
location.
Known Issues:
- Initializing or specifying a config file should persist those
changes back to the airshipui.json config file, so that the
chosen location can be read on app launch. It currently doesn't
- Once initialized or specified, the location of the config file
cannot be changed from within the UI
Change-Id: If2be1054c06ce0896179f3c43676a4e7cadcbe3a
e05b2efed0