Factor out the JSON format to its own page

[niemela]

Move the JSON format specification from "Contest API" to a new "JSON Format". This would give us 4 documents:

• CCS System Requirements
• JSON Format
• Contest API
• Contest Package Format

"Contest API" and "Contest Package Format" would both refer (and link) to "JSON Format" and could focus on their specific business logic. This would be very small changes for "Contest Package Format", but a larger simplification for "Contest API".

[deboer-tim]

FWIW we talked about this before, and I think I even tried implementing it but ran out of steam on some of the details. +1 though, if we can get it right it would be simpler and more logical overall.