Set IncludePaths via project property

[carlin-q-scott]

I'd like to include scss files from a particular library (Bootstrap) without having to reference the relative path to the files. If we were able to set the IncludePaths CompilationOption, then I could add the path to the library folder as a search path.

This would change:

@import "../lib/twitter-bootstrap/css/functions";

to

@import "functions";

The csproj config would look like:

  <PropertyGroup>
    <LibSassIncludePaths Include="/lib/twitter-bootstrap/css/"></LibSassIncludePaths>
  </PropertyGroup>