CC-5838: Editing a repeating show yields in error if an instance is in the past

Was not checking if show is repeating properly
CC-5343: Missing files can be scheduled via playlists

* Fixed it by adding a check for this.
updated translation resources
CC-5797: Install should give www-data permissions on stor

* chmod command was bugged due to extra 0 (read the docs)
Merge branch '2.5.x' of github.com:sourcefabric/Airtime into 2.5.x
CC-5588: Specific user can't see Library because ColReorder is null for
their account
CC-5867: Can't edit show instance
CC-5869: Changing a repeating show to non-repeating and changing start time does not work
CC-5833: Update airtime demo w/o o.p.s.
Fixed the unit tests and changed ops->zu
CC-5634: Can add/remove content to a linked show while one instance is currently playing
Merge branch '2.5.x' of github.com:sourcefabric/Airtime into 2.5.x
CC-5668: Weekly recordings get overwritten
Merge branch '2.5.x' of github.com:sourcefabric/Airtime into 2.5.x
CC-5756: Scheduler: Different results between Show contents and Add/Remove Contents
Merge branch '2.5.x' of github.com:sourcefabric/Airtime into 2.5.x
Merge pull request #59 from danielhjames/2.5.x

Remove INSTALL file, this information is more up to date in README
updated translation resources
Fix user session storage in multi-tenancy mode
Better session handling fix