Add documentation, build script, embeddable F# interactive

> NOTE: This is mainly for review purposes - the work is not quite done yet!

The aim is to make this proper F# open source project with the standard documentation & tools. The changes are:

 * Add FAKE build script to build everything, publish NuGet package etc.
 * Add documentation for some components (work in progress)
 * Add embeddable F# Interactive (`FSharp.Interactive.Service.dll`)
 * Rename the compiler DLL to `FSharp.Compiler.Service.dll`

The two work items that I still need to finish are:

 * Make sure that NuGet package is build properly
 * Add documentation for Editor & Embedded FSI