Bug 1082353 - Improve the job notation in the help panel

This work fixes Bugzilla bug [1082353](https://bugzilla.mozilla.org/show_bug.cgi?id=1082353).

This improves the layout and appearance of the job notations in the Help panel. Specifically, we:

* use a consistent character for all buttons
* include a statement of color rather than embed the color as the button label
* override a few of the default btn classes to paint all the buttons consistently
* add a job group button

Here's the before and after:

![jobnotationcurrent](https://cloud.githubusercontent.com/assets/3660661/4633763/4fe8fe10-53ca-11e4-82ca-c825a8b796d7.jpg)

![jobnotationproposed](https://cloud.githubusercontent.com/assets/3660661/4633759/4819af22-53ca-11e4-92e7-aa8be42df95c.jpg)

I've also switched the changed markup to use 2-space indentation, since we've agreed in channel to migrate all html in the repo from 4-space to 2-space indent. I figured I might as well integrate that change even if the file temporarily has a hybrid of both spacings. Let me know if it should be 4-space and I can switch it.

Tested on Windows:
FF Release **32.0.3**
Chrome Latest Release **37.0.2062.124 m**

@edmorley has signed off on the appearance in channel.

Adding @camd and @maurodoglio for review.