Rename admin flag on SqlAlchemy#stack_get

The `admin` flag was only used to avoid doing a tenant_id check between
the stack and the context.tenant_id, so it was renamed to `tenant_safe`
for better clarity.

Change-Id: I32c1156c8782bad39a265c77aad088c96400f69f
Closes-Bug: 1245952
Add a man page for heat-manage

Change-Id: I9b3d6b3b227ca2a2a2786837b941fdc420d3b2b6
Closes-bug: #1189651
Merge "Rename admin flag on SqlAlchemy#stack_get"
Merge "Add a man page for heat-manage"