Move get / set constraints into common directory
Move get / set constraints into common directory

This patch does three things:

1 - Moves the get/set-constraints code into the
common directory (see below).  The addition of the
get/set-constraints subcommands for environment
and service will be added as a separate commit.

2 - Removes the test dependency on mongoDB

3 - Changes get/set-constraints to be registered
as deprecated in 2.0 and obsolete in 3.0

As part of the hierarchical command work, there are
a few commands which can be under more than one super
command.  For example, get-constraints can be accessed
by both:

juju environment get-constraints
juju service get-constraints

To help organize these commands, the core functionality
will be moved into the juju/juju/cmd/juju/common
directory.  When possible, test dependencies on mongoDB
will be removed.

cloud-green/juju,kat-co/juju,makyo/juju,mjs/juju,tasdomas/juju,makyo/juju,anastasiamac/juju,mhilton/juju-juju,thomnico/juju,tych0/juju,tsakas/juju,cmars/juju,reedobrien/juju,AdamIsrael/juju,bac/juju,dimitern/juju,bz2/juju,cloud-green/juju,dimitern/juju,dimitern/juju,perrito666/juju,howbazaar/juju,thomnico/juju,ericsnowcurrently/juju,macgreagoir/juju,gabriel-samfira/juju,axw/juju,marcmolla/juju,cherylj/juju,bogdanteleaga/juju,gabriel-samfira/juju,perrito666/juju,wwitzel3/juju,perrito666/juju,frankban/juju-tmp,alesstimec/juju,cmars/juju,makyo/juju,mjs/juju,voidspace/juju,Altoros/juju-cloudsigma,mjs/juju,anastasiamac/juju,mhilton/juju-juju,dimitern/juju,alesstimec/juju,tasdomas/juju,bogdanteleaga/juju,howbazaar/juju,sinzui/juju,macgreagoir/juju,bac/juju,wwitzel3/juju,mjs/juju,bz2/juju,dooferlad/juju,alesstimec/juju,mhilton/juju-juju,tsakas/juju,mikemccracken/juju,reedobrien/juju,mhilton/juju,mhilton/juju,frankban/juju,bogdanteleaga/juju,cherylj/juju,frankban/juju,wwitzel3/juju,frankban/juju-tmp,gabriel-samfira/juju,ericsnowcurrently/juju,reedobrien/juju,fwereade/juju,davecheney/juju,kat-co/juju,Altoros/juju-cloudsigma,tsakas/juju,wwitzel3/juju,tasdomas/juju,gabriel-samfira/juju,cherylj/juju,perrito666/juju,fwereade/juju,mhilton/juju,thomnico/juju,mikemccracken/juju,ericsnowcurrently/juju,dooferlad/juju,frankban/juju-tmp,marcmolla/juju,bac/juju,sinzui/juju,AdamIsrael/juju,mjs/juju,bz2/juju,mhilton/juju,frankban/juju,macgreagoir/juju,cloud-green/juju,Altoros/juju-cloudsigma,frankban/juju,frankban/juju,macgreagoir/juju,macgreagoir/juju,davecheney/juju,Altoros/juju-cloudsigma,waigani/juju,perrito666/juju,fwereade/juju,anastasiamac/juju,kat-co/juju,axw/juju,axw/juju,waigani/juju,thomnico/juju,cherylj/juju,alesstimec/juju,anastasiamac/juju,anastasiamac/juju,tych0/juju,tasdomas/juju,bz2/juju,cmars/juju,bogdanteleaga/juju,tych0/juju,mikemccracken/juju,dimitern/juju,fwereade/juju,ericsnowcurrently/juju,voidspace/juju,kat-co/juju,ericsnowcurrently/juju,tsakas/juju,bac/juju,mikemccracken/juju,cloud-green/juju,kat-co/juju,howbazaar/juju,bz2/juju,reedobrien/juju,mikemccracken/juju,gabriel-samfira/juju,mjs/juju,mjs/juju,marcmolla/juju,alesstimec/juju,howbazaar/juju,waigani/juju,bac/juju,axw/juju,mhilton/juju-juju,AdamIsrael/juju,sinzui/juju,davecheney/juju,marcmolla/juju,voidspace/juju,tych0/juju,dooferlad/juju,AdamIsrael/juju,axw/juju,voidspace/juju,waigani/juju,makyo/juju,frankban/juju-tmp,dooferlad/juju,davecheney/juju,howbazaar/juju,cmars/juju,marcmolla/juju,sinzui/juju,dooferlad/juju,reedobrien/juju