Follow coding guidelines in ClusterComm
Start to move ClusterComm to JavaScript.
Merge branch 'sharding' of ssh://github.com/triAGENS/ArangoDB into sharding

Conflicts:
	arangod/Cluster/v8-cluster.cpp
Merge branch 'sharding' of ssh://github.com/triAGENS/ArangoDB into sharding
Allow /_admin/execute to return raw JSON.
Create empty _system database.
Fix double delete bug.
Slightly change documentation of API for ClusterComm::wait()
Add JS_Wait function for ClusterComm in JavaScript.
Merge branch 'sharding' of ssh://github.com/triAGENS/ArangoDB into sharding

Conflicts:
	arangod/Cluster/v8-cluster.cpp
Make global ArangoClusterComm object in each thread.
Fix name of global object ArangoClusterComm.
Merge branch 'sharding' of ssh://github.com/triAGENS/ArangoDB into sharding