adding admin subnet
Merge pull request #490 from edx/jarv/add-admin-subnet

adding admin subnet
Don't do migrations.
Externalize migration settings.
Set scaling group limits to match desired capacity.
Fix json typos.
Merge pull request #494 from edx/feanil/stage

Feanil/stage
removing basic auth credentials.
Merge pull request #496 from edx/e0d/remove-basic

removing basic auth credentials.
Make basic_auth a global nginx parameter

Instead of enabling basic auth per role this makes it
an nginx parameter which makes more sense for sandboxes
and probably other servers where we want basic auth turned on
Merge pull request #497 from edx/jarv/better-basic-auth

Make basic_auth a global nginx parameter
adding option to enable basic auth when we provision
Merge pull request #498 from edx/jarv/basic-auth-provision

adding option to enable basic auth when we provision
Allows override of nginx configuration templates via simple variable
Allows override of nginx configuration templates via simple variable
(cherry picked from commit bc8f6f86d3d1df48ada16cad98b0e8af3d3669dc)
Correcting bad merge