Use direct accessors for attribute/relation grabbing in programmes feed API generator.

Time for cleared caches -> full output finalised
Before:
9406
9344
9358

After:
5048
5067
5122
Directly grab internal attributes array to save on logic we don't need when generating simple data caches.
Use direct internal array grabs for revisionable and programme data also.
Update to apply new logic to attributes i missed first time around.
More minor improvements
Avoid pulling back unneeded data (and making laravel hydrate it)
Override get_attribute in revision model to allow direct array usage rather than array_get to return values.
Moved missed data attribute to proper get_field method.
Add faster get_attribute to simple data to try and improve performance a little in xcri
Add direct array access within front page loop to try and avoid the long page load (when theres a lot of data)
Add migration to fix index (we renamed a key and didn't update the index)
Merge pull request #258 from unikent/feature/use-low-level-features-for-speed

Improve cache generation speeds.