CC-5733: RESTful API data sanitization and validation

Validate field types on post/put requests using the EditAudioMD form
Merge branch 'cc-5709-airtime-analyzer' of github.com:sourcefabric/Airtime into cc-5709-airtime-analyzer
CC-5733: RESTful API data sanitization and validation

small fix - was setting the hidden flag twice
CC-5709: Airtime Analyzer

* Catch bad callback_url
Merge branch 'cc-5709-airtime-analyzer' of github.com:sourcefabric/Airtime into cc-5709-airtime-analyzer
Merge branch 'cc-5709-airtime-analyzer' into cc-5709-airtime-analyzer-saas