Moved common widgets to common module
Moved common code to util package
Removed unused code
housekeeping
added link to model
Added first prototype of link editor
Wired editor to back-end
Removed name attribute for link 
Added value visualization for link
wired code links loading
Made Group generic
Introduced Attribute Group
Added link group
fixed link groups
Modified update model
Sync changes with central grid
Functions arguments are now retrieved from backend
Added scroll for links and link types
Fixed links creation and editing
Other fixes
Fixed value update
style updates:
- new link icons
- restyled attribute edit dialog
- restyled sidepanel button bar
Moved links and linktypes panel common code to a common panel
Made link intances not editable
Merge branch 'linkinstance' into dev
Fixed group cloning