Change the default goto declaration to default to the code declaration rather than the signature file

Ideally we would toggle between the two but there is an issue in FCS
where if you are in a signature file there is no way to get the
definition file.  See
https://github.com/fsharp/FSharp.Compiler.Service/issues/134
Removed signatureIndenter and summary split lines these are mangled by indentation and line feed processing upstream
Fix CodeDom so that invalid keyword identifiers are corrected

See https://bugzilla.xamarin.com/show_bug.cgi?id=17658

The current mechanism is to use an ‘_’ prefixed to the id, we could
change this to ``identifier`` if we wished, although this would require
regression testing all other uses of the (-!) function.
Merge pull request #513 from 7sharp9/master

Fix CodeDom so that invalid keyword identifiers are corrected
Merge pull request #515 from fsharp/master

merge changes from  master