mongofiles doesn't support chunksize

The mongofiles tools has a few deficiencies:

• the collection parameter is ignored
• it makes implicit assumptions about collection suffix (".fs")
• it does not properly delete chunks on replacing a file, but only the meta data, in the worst case it can even delete chunks of an unrelated file
• the chunk size cannot be specified, it only ever uses the default size

A patch set fixing these issues has been submitted as Github pull request #471 which fixes all of these issues.

Related bugs which describe one or another of these problems:

• SERVER-4931
• SERVER-2334
• SERVER-6874
• SERVER-2335
• SERVER-2469

As per request in the pull request I'm opening up a new ticket describing the pull request as a whole.