issue #128
RESTCOMM-628
 - Added new 'script' RVD element in the UI
 - Added backend support for 'script' element for groovy source code
 - Advanced RVD project version to 1.2 to cater for new element syntax
issue #128
RESTCOMM-628

- Improved the internal data structure used for storing variables. Variables are stored as InternalVariable
objects instead of plain strings.
- Added support for passing/retrieving variables to groovy scripts. Collect and ES elements have been reworked.
- Tested various callflows with collect/es/script elements succesfully
- TODO - remove the old 'variables' structure
issue #128
RESTCOMM-628

Updated all verbs so that they use the new variables structure