Implementation of a Receiver and Service to provide for the capability

to accept control from other Android applications.  Allows for
changing both Account-level and global settings.  Account-level
settings can be applied to a single Account or to all Accounts.

The file class file derived from src/com/fsck/k9/K9RemoteControl.java
will be bundled into a JAR file for use by external applications.

This facility will be used for:
Issue 215
Issue 730
Issue 864
Issue 884