- add Settings: Activity to start / stop MPD Service (Main).

- Main is a service that run in foreground with a notification. See
  Service.startForeground documentation for more details.

- Main.Client is used to control the service: start or stop it and also receive
  callbacks when service encounters an error, is killed, is started or is
  stopped.

- Main.start to start the service without any fallback.

A Java object to send logs on the android side.

javah is deprecated.

Eliminate a use of GetGlobalConfig().

The number of MPD installs on Android < 5.0 is negligible, and that
API version introduces lots of useful features for MPD.

Fixes problems with the Windows build because `-DCURL_STATICLIB` was
missing, causing error messages like:

 "undefined reference to `__imp_curl_slist_free_all'"

Changed listen_add_config_param() to use generic address parsing

Was converted to reStructuredText / Sphinx in commit
8a689e68

Migrating from DocBook to Sphinx.  Editing XML is really too
cumbersome.