Fixed bug in login as other user.

1) Autocomplete js issue. Added in assets application.js so not needed to include again.
2) Changed to get email instead of id from params.
Changed the object label method to pincode. This used as display method in all the places.
Fixed the pincode display issue.
Already used pincodes are not shown in the pincode list.
Changed Center name to be read only in edit for all users except super admin.