Add additional web file formats for Content

Added:
  - .less
  - fonts
  - .svg
    - Included as its own entry since it's not strictly an image format
Add more common web content types

SASS http://sass-lang.com/
Stylus http://learnboost.github.io/stylus/
Merge pull request #554 from bryanhelms/more-web-build-actions

Add more support for common web files as Content