Revert "Removed admin and client models."

This reverts commit 9b5bea3fca3ad45c77e7a71a99dc3f185ab43d7d.
Revert "Removed devise_for in routes for clients and admins."

This reverts commit 35bd42d6a1f034e70ff1188c11aedd8b2325ad29.
Removed clients and admins.