Documentation Cleanup

I noticed that the website theme for the F# Charting library has diverged from the other sites in the group: Deedle, R Provider, F# Data, and F# Data Toolbox. Most notably, it doesn't contain the links to those other sites in its header, although they link back to it.

Therefore, I copied the header from those other sites so that you can navigate back and forth between them. I also updated the CSS from the F# Data site so that styles are the same. As I was doing this I decided to make some small cleanups throughout the documentation. You can read the detailed messages for each commit. I tried to order to the commits from least controversial to most so it is easy to throw out any ones you don't want.

Only remaining problem is that I couldn't find the large logo for F# Charting that should be displayed in the upper portion of the sidebar like the other sites have. I'm pretty sure such a logo must exist because the other sites are using a thumbnail version of it to link to F# Charting.

You can preview what the new generated site would look like [here](http://lasandell.github.com/FSharp.Charting). Compare that to the original [here](http://fsharp.github.io/FSharp.Charting/).