Make partial sleeps at least validate for uniqueness
Adds a weak and rather user-unfriendly validation to the javascript
entry.

[There should be no way a user can enter a sleep that overlaps with
another sleep now]
Fixes bestByTime caches for groups, derp.
Moves header/footer block tags outside of cache tags in frame to allow overriding.
Merge branch 'master' into groups

Conflicts:
	zscore/templates/frame.html