Add "parent" key to list stacks output

Pass back the stack owner_id (parent stack ID) via the RPC API, then
expose it via the "parent" key when listing stacks.  This will be
None for all top-level (non nested) stacks, so can be ignored when
show_nested is not passed.

blueprint: list-nested
Change-Id: I5ad7f867bc7eb138bf2d7d17b4a3bf810d341393
Fix usage of environment section constants

Previously, constants were not being used or were being defined in
multiple places.

Change-Id: Iddd001392b77ac57d858a84daba66553a90465b2
Add length constraint to Nova Keypair's name property

Sets min/max bounds of the Nova Keypair Resource's name
property to 1 and 255 respectively.

Change-Id: I48fb25eee465938fd7e48e105187d1646c8c64c0
Closes-Bug: #1303865
Merge "Add length constraint to Nova Keypair's name property"
Merge "Add "parent" key to list stacks output"
Merge "Fix usage of environment section constants"