Added a new definition for general language model management

This can be used for grammars, ngrams, and keyword spotting.
This will replace current grammar management definition.
Add the new grammar management message CMakeLists

Also changed the definition of ASRSrvRequest to deal with this new
general definition.
Grammar manament message removed.
Merge pull request #3 from jordiadell/rosapi2.1

Modification of the ASR ROS API to 2.1