Add event: Temperature

[avluis]

When a temperature has been set, trigger an event (for notification, for API push, etc).

I believe it should come in handy for those time when the heated bed is taking its time to reach temperature.

Note: It would be best to have conditionals so that it only notifies if it has been set manually and not every time a gcode file tells the printer to got to a certain temperature.
On the web UI, you could have a notify me checkbox next to the set temperature button if this ever reaches interface level.

[jonaslorander]

I belive this question is better suited in the OctoPrint hub;
https://github.com/foosel/OctoPrint

[avluis]

Got it, will delete and add there!
And reading the issue tracker, it looks like it is already there.