Errors are now underlined on request.

However strings are not underlined even if they are an error.
Preferably this would occur automatically.
Better colouration would be nice.
Hovering over the error should give the error text.
Add jump to definition with test

This needs some tidying! E.g. refactoring of syntax splitting.
Update for prettier error underlining, also needs face to be moved elsewhere perhaps.
Sample of working project-loading for .NET 4.5. This might be integrated later.
Added emacs support for jump to declaration