Added a bit of explanation for GeoCouch query mode.

Because I am still bored. Nothing to do now but sit and wait and read blogs in
the internet and wait for more paychecks. Awesome!!!
Wrote some comments for each map/reduce function.
Enhanced control-flow comprehensiveness in some map/reduce functions.

Wow this must look like serious work!!
Moved _list/bbox-filter/bbox callback into named function.
WIP: This was supposed to be ready ad 4:30p.m. I suck at this.