Add an option to global set the possible hours of message sending.

Currently, if we queue a lot of sms to send, the device can send them at late evening or even night. This feature can limit the hours of message sending, it can be similiar to shift management which is part of current software, but more global, not limited to contacts.

Migrated from the SMSEagle UserReport forum (2017-11-27). Legacy status: Completed.