Delete a link to the now obsolete stable version.
Merge remote-tracking branch 'origin/master'
Major refactoring efforts on renderer API.

- Remove assumptions for a grid style UI.
- Separate the callback interface from the renderer API.
Update libraries to the latest version.
Fix wrongly escaped property name in expression error message.
Remove /etc from the folder selection tree.
Fix launcher shortcut links and messages.

- Currently, labels are hard coded as Pentaho doesn't translate 
them in launcher overlays.