Remove support for the old API in fix_widget_code
Remove old-context-test widget
Remove old API file
Remove VariableGadget.js
Remove get_old_widget_api_extensions
Remove support for event and slot variables
Remove support for the old context api from javascript
Remove _annotate method from the endpoints code
Remove test_basic_ezweb_widget_creation
Rework preference support removing old API structure
Remove support for unused template features (now that the old API is not supported)
Remove ContextOption model
Merge branch 'remove/old_api' into develop
Add Subdata tree functionality

Signed-off-by: Álvaro Arranz <aarranz@conwet.com>