Allow wakeup calls to be managed via GUI

Recent commit has wakupcall management (schedule/delete) working from the FreePBX module admin page.
https://github.com/POSSA/Hotel-Style-Wakeup-Calls/commit/9021fff26ebbc79bce38e8df0db1cecfc717d326

Issues:

1. I need some validation of the schedule call data so that no call is scheduled if missing info, need to default minutes to 00 if not provided and force hours to 24 hour time format

2. Current code prepends wuc. to all .call filenames so they are distinguished from .call files scheduled by any other means. The GUI only lists .call files with the wuc. prefix.