Use MongoClient override rather than Mockito

use Objenesis to construct an instance of MongoClient and simply
override the necessary methods. Also, now using MongoClient rathar than
Mongo.
prep for 1.2.0 release
[maven-release-plugin] prepare release 1.2.0
[maven-release-plugin] prepare for next development iteration
distinct can take value from path
merge from master
merge