Restyle treeview to be more like the solution explorer.

[JoshVarty]

Since we're using that metro treeview, it's a little generic.

I'd like to style it similar to Visual Studio's solution explorer:

• Folder images for folders
• Appropriate images for .cs and .vb files
• No animation, or at least no slow fade animation like it has now. (It feels slow)

[AmadeusW]

As we're doing this, I'd love to remove the dependency on MetroUI. This library added hundreds of css files into our Content directory and makes working with the header very difficult (I had to use !important to correctly position the logo on the home page.)

I've already recreated the header using plain bootstrap for the code browsing pages. I'd like to clean up the whole CSS when we have a chance.