Add ability to exclude certain files

[zastrowm]

We use another extension called Xaml Magic which reformat xaml nicely (with a lot more options than Resharper). But using "Format on Save" with you extension also reformat (with a different rule set) xaml files. So could you let the user pick which file extensions should be reformatted on save?

[zastrowm]

It'd be really nice to be able to leverage editor config for this somehow. From the discussion at editorconfig/editorconfig-visualstudio#45 ReSharper is adding support for editor config, so maybe we can work off of that?

It also seems as if Visual Studio itself might incorporate editor config