Use explicit availability flag to compute simple location availibility

Instead of relying solely on availibility window simple location
availability takes an explicit flag into account in conjunction with
the window.

The availibility window will also use the *actual* availibility start
time over the availibility start time if it's set.
Merge pull request #100 from atlasapi/mbst-4456-location-availability

Use explicit availability flag to compute simple location availibility
Add an activelyPublished flag - indicates whether we are recieving information about a piece of content from it's publisher. Defaults to true.
Merge branch 'master' into mbst-4791-lovefilm-deletes
Merge branch 'mbst-4791-lovefilm-deletes' into stage