Improved sanitization

Widget bundle is now sanitising all fields and it performs sanitisation
before previewing a widget.
Updates for 1.1 release.
Added default widgets.

Added a list of widgets that will be active as soon as the plugin is
activated for the first time.
Added empty check for repeater sanitisation.
check if markers_draggable defined in maps widget for template variables.
Merge branch 'master' of github.com:siteorigin/so-widgets-bundle
Merge branch 'master' into develop