feature/477: Creating Walkthrough default widget

* adding new library: reveal.js - recompiled in order to work fullscrren as we need it
* adding gulpfile for compiling sass files
* modifing iframe template to use the new library
* modifing walkthrough_slideshow module, to load slideshows when there are no screenshots
* adding new iconfonts (extending the existing ones, generated with icomoon webapp)
feature/447: default widget fixes.

Fixing errors from previous commit.
feature/477: default walkthrough widget.

fixing errors from previous commits.
Merge pull request #67 from csanyiarpad/feature/477-walkthrough-default-widget

feature/477: Creating Walkthrough default widget