Add ModuleFactory#getDefaultModules method to config-api.

Add ModuleFactory#getDefaultModules method to config-api.

Add method to populate pre-existing state. Modify code generator to generate
a blank implementation. Calling of the method is done by config-manager
every time new ModuleFactory is discovered in OSGi service registry, each time in a separate transaction.
Implement default module functionality in config-manager.
Add DependencyResolverFactory for default modules to be able to lookup dependencies.
Implement new service tracker tracking ModuleFactory instances in order to commit blank transactions
every time ModuleFactory service appears or disappears.
Clean up pom versions: merge config.yangstore.version into config.version.

Change-Id: I47229c9e403b817b24740c8f77ad43abcc720094
Signed-off-by: Tomas Olvecky <tolvecky@cisco.com>