Add parameter to handle "storage" options

[twillouer]

Hi,

thanks for your work.

I'm looking a way to handle parameters like "storage" (https://docs.mongodb.com/v3.4/reference/configuration-options/#storage-wiredtiger-options)

Especially the parameter 'storage.wiredTiger.engineConfig.cacheSizeGB'

I didn't see how to handle this by now, is it possible to add a parameter ?

[kujeger]

As a workaround you can do this in hiera:

mongodb::server::config_data:
  storage.wiredTiger.engineConfig.directoryForIndexes: true
  storage.wiredTiger.engineConfig.cacheSizeGB: 10