Support sending writeConcern for commands that write

When talking with server 3.4 or greater (maxWireVersion >=5), writeConcern should be a supported option for commands that write.
Helpers for the following commands therefore must be updated to support the option. The list is ordered according to likelihood that a driver has a helper for the command.

• aggregate with $out
• copydb
• create
• createIndexes
• drop
• dropDatabase
• dropIndexes
• mapReduce with $out
• clone
• cloneCollection
• cloneCollectionAsCapped
• collMod
• convertToCapped
• emptyCapped
• renameCollection
• appendoplognote
• godInsert
• capTrunc
• reindex
  * mergechunk


Note:

When the writeConcern on a command that writes fails, the resulting document still comes back with ok: 1. Hence, to check for write concern and raise the appropriate error to your users, you will need to check the resulting document for a writeConcernError field. If it is present, then writeConcern failed.