Added a deadline for hearbeat update (60s and 30s respectively) and bumped up garbage collection deadline to 90s.

The garbage collector now sets a flag on the agent object indicating garbage collection.
The process will immediately exit when detecting garbage collection.

The full list is still available in a serie of log lines.

This reverts commit a3c278a5

Some typo fixes.

In order to be efficient, the data (tape status and queue sizes) is cached in memory.
This function needed access to the catalogue (where the tape status is located).
This in turn required passing the catalogue object to:
 - The garbage colletion functions for all object types.
 - The garbage collector object now keeps a reference to the catalogue.
 - The path to the catalogue credential file should now be passed to cta-objectstore-collect-orphaned-object
 - The OStoreDB also needs a reference to the catalogue in order to queue retrive requests.

 The garbage collection member function are now also being passed a log context, so the requirement for better
 log of object fate can also be fulfilled later. This in turn required the passing of a logger object to
 the object store and relative helper classes.

 Finally, a dummy catalogue class has been created to be used in unit tests.

This required to pass an AgentReference through to all garbageCollect() member functions of all objects.
The changed behavior required adaptation of the corresponding unit test (the archive queues now need to
be properly referenced in the root entry).

We now use protobuf's introspection to dump objects into JSON instead of ad-hoc code
using json-c.

Implemented Agent::garbageCollect()
Made AgentWatchdog fetch the timout from the agent object.
Fixed unconditional time tounter reset in AgentWatchdog::checkAlive()
Fixed missing log for garbageCollection.
Added utility (cta-objectstore-unfollow-agent) to mark agents as not followed when they get orphaned. This utility detects looping ownerships (two garbage coolectors watch each other and both die synchronously). This utility is not packaged.
Various log improvements.

Added missing garbage collection for all object types.
Added logging to AgentHeartbeat.
Some object types still miss garbage collection implementation.

Agent becomes a usual class, like any other in the object store.
Object name generation (agent's and others) is now handled in the separate AgentReference.
The previous situation created race conditions.

ObjectOps by adding a second parameter to the template.

Thanks to Steve Murray for findind the solution.

Partial implementation of per object type dump.

Corrected a typo in hpp filename and added content for OStoreDB::queue(const RetrieveToDirRequest& rqst)

The agent now carries its own timeout (defaulting to 60s).
The unit test now validates that the 2 agents were cleared from the agent register.

Added support and unit test for object creating calls in RootEntry (DriveRegister, TapePool, AgentRegister)

Added support for creation of tape pools and agent register and created a unit test for agent register creation.

Renamed the setName/GetName functions to the more appropriate getAddress/setAddress.

Created a richer protocol buffer RootEntry object and created a parital implementation to allow unit tests to run.

middletier, itself separated in interface, SQLite, objectstore and
shared tests.
Moved all utilities (exceptions, threading...) to a shared utility
directory.
Created a single, shared unit test from all the scattered ones.

License comment is no longer filtered out by doxygen when generating web pages of the individual source files.

Implemented the self registration and unregistration functions for the agent.
Improved the safeguards and imlpemented more initialize() function for different object types.

and created initial unit tests for those.