Add icons to the backend iconfont

Note: If you don't feel comfortable adding or removing icons yourself, please contact @yellowled before making changes.

General hints

Please use Fontello
Please stick to the FontAwesome iconset, do not mix it with other iconsets.
Always start by importing the current iconfont selection (see first step below).
If you need to remove icons from the selection, make sure to replace them – with different or new icons – in the backend templates.
Please only add icons you definitely need in the backend, no “I might need this or that some day”. It's a performance issue.

Click the wrench icon in Fontello and import templates/2k11/admin/font/config.json.
Once you're done adding and/or removing icons, click “Download webfont”. Extract the downloaded zipfile and copy the following files to templates/2k11/admin/font/, replacing the current ones:
- config.json
- font/fontello.*
In templates/2k11/admin/style.css find /* ICON FONT. In the CSS segment right after that, replace the number in the url atrributes in that block with the number from css/fontello.css in your downloaded zip file.
In templates/2k11/admin/style.css find the block with all the icon declarations (.icon-home:before { content: '\e800'; } etc.) and replace that whole block with the contents of css/fontello-codes.css from your downloaded zip file. Please remove the comments at the end of each line.
Any time you save templates/2k11/admin/style.css, please make sure that it's ISO-8859-1.
Commit this seperately as “New icon font build”.
Add/edit the added/removed icons to/in the backend templates. Commit your changes seperately.