GPII-259 Initial source code of the Xrandr Node.js

[Includig]
  - Adding the add-on structure.
  - A brief demonstration of how this add-on should be used is included
    into
    nodexrandr_tests.js file.
  - Adding a getDisplays method. It returns some information about the
    displays.
  - Adding a getBrightness method. It returns the current brigthness
    value.
  - Adding a setBrightness method. It sets the brigthness level.
  - Adding a dummy setScreenResolution method. Still requires some work.
GPII-259: Implementing setScreenResolution method
GPII-259: Adding jqUnit tests for the Xrandr bridge
GPII-259: Creating an Xrandr Settings Handler

[changes]
- Adding:
  - gpii.xrandr.getBrightness
  - gpii.xrandr.getScreenResolution
  - gpii.xrandr.setBrightness
  - gpii.xrandr.setScreenResolution
GPII-259: Adding the xrandr module to be loaded at start
GPII-259: Adding a few jqUnit tests for the Xrandr Settings Handler
GPII-259: Include the Xrandr add-on into the build system
GPII-259: Code cleanup
Merge remote-tracking branch 'javihernandez/GPII-259'

Conflicts:
	build.sh
	clean.sh
	gpii.js