Eliminate remaining uses of @Named("appName")

Changes include:

 - Introduce ViewCB#TITLE_KEY for use in setting the title of the
   notification windows (see it used in MainViewCB).

 - Remove lighthouse.files.AppDirectory. Several methods from this class
   have, as of this commit, been rewritten and moved into the
   BitsquareEnvironment and BitsquareApp classes as appropriate.

 - Rename "appName" property => "app.name" for consistency with other
   configurable properties.

 - Allow configuration of both user and application data directories on
   the command line. See --help menu for details.