Add notification system

[jimboca]

Adding notifications for pushover, pushbullet, ... are very tedious using the ISY network module so I would like a simple notification system.

Something simple like:

notify:
variable: SomeVariable
values:
1 "This variable is one"
2 "This variable is two"
* "This variable is <>"

First plan to use pushover since that's what I currently use and it works best in Takser, but will look at other methods, and will consider others if anyone else has inpute.