integrate KAT into MathHub

[kohlhase]

It would be great if we could use KAT for casually producing OMDoc markup. For that KAT needs to be integrated into MathHub first. This is the MathHub-side tracker bug, to be used for planning, the KAT-side one is https://github.com/KWARC/KAT/issues/47 cc: @tkw1536 @LiftnLearn Here are the things that should be done MathHub-side (most of the steps need to be elaborated considerably).

• accept HTML5 as a surface language (see #99)
• add the KAT JS into the served pages.
• store the RDF annotations from KAT
• make an interaction to harvest the RDF and create OMDoc from it and store the OMDoc.

[tkw1536]

This will likely require a lot of work, since the old-style javascript from KAT depends on the old JOBAD and will not simply be integratable in the new MathHub,

[kohlhase]

closing.