Allow to use the MongoDB runcommand on a collection

[lgomezma]

Right now I believe that the mongo adapter doesn't allow to execute a runcommand on the model collection such as 'geddy.model.Mymodel.runcommand'.

The runcommand is used for example in the new Text Search feature of Mongo 2.4.

[lgomezma]

Also runcommand would be useful to allow the use of Mongo's aggregation framework.

[mde]

We're using the MongoDB wrapper (https://github.com/idottv/node-mongodb-wrapper) as an intermediate layer. I can't see at a quick glance how that would work. I'll have to dig a little more in the client code.

[lgomezma]

MongoDB wrapper has a runcommand in the collection here https://github.com/idottv/node-mongodb-wrapper/blob/master/lib/Collection.coffee#L38, maybe we could add a runcommand in the mongo adapter that would run the runcommand from the wrapper. I'm trying to write it but still trying to figure out how the query argument works in the adapter...