*Add a Pause/Continue button for job.

=>It's very usefull to pause a job. User can : change the PLA/ABS, modify printer configuration, heater, or just AFK the printer for Xmin and Continue the current job after, without any issue

*See Server Commit for more details
*Add a Pause/Continue function for Repetier-server

Allow the user to pause a job, and continue it later.
The printer memorize x/Y/Z/e/F/Temp before the Pause, and set them when the job Continue/Restart.
**The printer wait for the memorized_temp to be reach before continue the job.
**The head move z+30.0 when the Pause start => prevent the hot PLA flowing out.

WHAT NEED TO BE CHECHED :
	Start a job when another job is Paused.
	Does the Server call the Pause Script when the pause is set (It should be be i didn't check)
	Improve the PLA Flowing out handler. Extract more when paused ? Move more the end ? Inform the user about this prob. ?