set key expiry properly for scheduled maintenance spanning current time
Merge pull request #634 from flapjack/sched_maint_expiry_bug

set key expiry properly for scheduled maintenance spanning current time
fixes #637 - GET /media/id works for sms_twilio now
Merge pull request #638 from flapjack/637_jsonapi_get_sms_twilio

GET /media/id works for sms_twilio now
fixes #639 - expose newer media types in /edit_contacts
Merge pull request #640 from flapjack/639_webui_sms_media_labels

expose newer media types in /edit_contacts
Merge branch 'master' into 623_purger
minor refactor as per @ali-graham's suggestions