Match multiple-job pin key modifier to TBPL (1033266)

This work fixes Bugzilla bug [1033266](https://bugzilla.mozilla.org/show_bug.cgi?id=1033266).

The event `ctrl+LMB-click`, now pins the selected job to the pin board. If no job is under the mouse event the method is bypassed. I've tested a variety of jobs, with both Firefox and Chrome and the switch over from `shift` to `ctrl` appears to be behaving as expected.

I've updated all the help and documentation, and I think I have found all occurrences. It would be good to sanity check that in the review. I've included mention of the recent change for `spacebar` pinning, where applicable.

Tested on Windows:
FF Release **30.0**
Chrome Latest Release **35.0.1916.153 m**