Mongo_Toolkit: enable execution of all mongo methods

[epignatelli]

We currently force the use of the aggregate method, which is just a small part of the mongo methods collection. Enabling methods like count, replace, update would simplify things.

We can take two ways:

• Have another Query object, that specifies the command
• Use the Execute method in the bhom to send custom commands.

I lean towards the latter, as it is a more advanced feature, which could compromise the database.