3468 update help link and tiny icons

http://code.google.com/p/otwarchive/issues/detail?id=3468

* Adds custom icon font in multiple formats mapped to Unicode's private use area
* Updates HTML and CSS to use icon font to create restricted lock icon, hidden by admin lock icon, RSS icon, email icon, and help icon
* Includes IE7 and (probably) IE6 fallback: while the icons do not display, the landmark text becomes visible (e.g. the word "Help" displays instead of the icon; the exception is the RSS icon, where the icon is purely decorative and "Subscribe to Feed" is always visible, thus the fallback is unnecessary)
* Removes the RSS icon from the imageset file
* Adds a PSD of the imageset file so we're not constantly re-saving an increasingly-compressed version of the same image

**Note:** The font is licensed under CC BY-SA 3.0, which means we need to attribute it. The easiest method would likely be adding an FAQ section, which requires admin attention. The creator of the font says:
>A mention like "Entypo pictograms by Daniel Bruce — www.entypo.com" is considered acceptable attribution.