Search box tweaks: replaced button for search box with custom button

The search button was impossible to style on the Ubislate tablets, and messed up all the formatting (shifting down, overlaid on other page content, etc). After spending 2 hours trying to style it such that it looked ok on both "real" browsers and that browser, I gave up and just made it a custom button. Looks like this (on both browsers!):

![image](https://f.cloud.github.com/assets/618416/1636679/f7eb789a-57d6-11e3-8f6d-6d194ef2ed2b.png)