Added support for Roslyn rename options

[filipw]

This PR introduces support (via omnisharp.json and the rest of OmniSharp configuration model) for Roslyn renaming options.

{
    "RenameOptions": {
        "RenameInComments": true,
        "RenameOverloads": true,
        "RenameInStrings": true
   }
}

The solutions builds upon the original workspace options extensibility created for FormattingOptions. The options are respected in real time - changes are propagated to the workspace without the need to restart OmniSharp.

Following options are supported (all of them are switched off by default and need to be enabled explicitly):

RenameOverloads

RenameInComments

RenameInStrings

I will update the documentation https://github.com/OmniSharp/omnisharp-roslyn/wiki/Configuration-Options once this is merged.

[filipw]

since this was approved I will merge it - I will have a separate PR soon touching similar code and don't want to get into conflicts and keep this open