Style code & code cleanup

* Remove sprockets-stylus leftovers
* Adjust code style guidelines
* Reformat Rakefile
Remove UI classes
Add missing SCSS depend / update icons
Cleanup assets
Prepare for multi-soruce boards.
Include asset dependencies as files in development
Experiment on backbone client frontend
Extract shared sprocket environment into lib file
Cleanup board browser spec
Do not longer use .rdb-handle; fix utils
Drop icomoon - use FA instead.

* Adjust font-sizes, theme and paddings
Adjust templates
Remove desktop FA font file
Finally found a fix fir missing sprockts directives.

* MRI >= 2.0 + 3 years old software... 
  ...required by exact version by rails 3.2
Add Sprocket::VERSION check to patch