Bug 4105: Add dynamic module/shard config for entity-owners shard

Added a new method addModuleShardConfiguration to Configuration.

I simplified the internals of ConfigurationImpl to make it easier to
add a new module/shard config. I combined serveral of the maps into one
moduleConfigMap and reduced the total # of fields to 3. For
synchronization, I kept the maps/sets immutable and used copy-on-write
semantics to update them as they will seldom change. I also made the
fields volatile.

I also removed the singleton nature of ShardStrategyFactory since each
datastore's Configuration will now be different, ie only the operational
datastore's Configuration will have the entity-owners module. The
datastore's ShardStrategyFactory instance is not instantiated and owned
by the ActorContext.

To make things easier for unit tests, I abstracted the file-reading code
in ConfigurationImpl to a new ModuleShardConfigProvider interface and
FileModuleShardConfigProvider implementation in the config package.
I also moved the inner classes to the config package.

While I was at it I also moved Configuration and ConfigurationImpl to the
config package for consistency.

Change-Id: I1d6858d3ae68869ca6f61d4f5a5f0d319d93c485
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>