currently namespace options is embedded in the tooloptions struct.
this is a problem because:

• it forces mongostat to have arguments for --db and -c, which makes no sense.
• it forces mongofiles to have a -c argument, which makes no sense because mongofiles only works within a database and not a single collection
• probably other similar cases that i haven't thought of.

we should probably just split the namespace options out, and have it be explicitly included only by the tools that need it.