Fixed compilation issues with -pedantic (added  -Wno-long-long for protocol buffers generated code).

Added host to UserIdentity so that the authorisation of adminstrators can be based both on the user and the host from which they are communicating.

Each of the methods of cta::ClientAPI need to know on behalf whom
the request is being made.  This user-identity information is
required in order for the tape archive system to be able to
authorize requests.

Removed needless compilation of MockClientAPITest from the client library and also renamed the unit_tests directory to just test

In order to simplify development, we will not turn the types into numbers.

Intermediate commit: started to implement the garbage collection, plus a producer and consumer action.
The Agent class is becomming too complex, so started to split it up between the current agent (living with the application it represents)
and the AgentVisitor, which will look at it from the outside (for the garbage collector).

Moved objectsore classes in cta::objectstore namespace (and protocol buffer serializers into cta::objectstore::serializers).

Improved agent name layout.
Added printouts in test program.

Removed unused intent logs, implemented automatic agent registration with proper intent logging and added further dumps.