Add ability to add all devices to a schedule

[seanmancini]

Right now if you have alot of devices its cumbersome to add them to a maint schedule
It would be nice to be able to assign a device template to the schedule without adding specific devices

[astrayel]

I guess this one too is resolved with the ability to add an existing schedule to a device with device link or dropdown menu in device list.
See commit 2521a40.