Changed XML schema.  Added ArgumentType and MessageType class.  Preparing to add better BaseMessage construction.  Improved tests to include better code coverage.
Renamed BaseMessage class to Message.  Changed to reflect MessageType including new constructor by name.
Removed uses of Message(short id, Object... args) constructor except in MessageOutputStream.
Moved non-client-specific classes into com.jenjinstudios.message
Moved non-client-specific classes into com.jenjinstudios.message
Moved SQLHandler into com.jenjinstudios.sql
Updated MEssages.xml, added ExecutableAESKeyMessage and ExecutablePublicKeyMessage classes.