Various Menu Appearance Changes

Added hover background color for the navbar gamemodes list
![gamemodes_list](http://i.imm.io/12VEF.png)

Added padding and placeholder text to search boxes on new game and gamemodes list menus. This makes it easier to spot for new players. If you take a look at the css and notice I used the class ".searchbox" for the gamemodes list, it's because the css from the newgame menu was conflicting.
![newgame_search](http://i.imm.io/12VGn.png)
![gamemodes_search](http://i.imm.io/12VIM.png)

Aligned 'Install Gamemode' to the right side of the server list. Now it doesn't look so awkward being place at 50% width. I moved the search box down just a tad.
![gamemodes_install](http://i.imm.io/12VPX.png)

I'm testing each change I make in both the latest version of Chrome and an Awesomium WPF example application using v1.7.