Adding support for MongoOptions

Support for `MongoOptions`, added tests for the same. 

The MongoOptions that can be supported are `socketKeepAlive` (false), `socketTimeout` (0), `connectTimeout` (10000), `connectionsPerHost` (10), `threadsAllowedToBlockForConnectionMultiplier` (5). The (default) values have been taken from the official MongoDB documentation.

This will enable the plugin users to tune the `MongoConnection` being used by Salat.