Introduced editor (VS2012 only) part 1

Due to limitations with Premake the editor is currently only available
for Visual Studio 2012. Hopefully Premake will be updated with the
required features and this can be solved.
The introduction of the editor required quite a few changes, which
reached farther then just the editor. Most notable are the commandlets
that are now made more generic in the form of tools, the command line
version requiring less typing to execute tools and tools being able to
execute different actions.
Introduced editor (VS2012 only) part 2