Eclipse Sprotty 0.12.0

This release is focused on stablization and bug fixing. Rather than adding new features the main changes of this release are general clean up and bug fixes. The main changes are:

•  Consistent removal of hover feedback
•  Improve extendibility of `ElkLayoutEngine`
•  Fixed an issue with the `CommandPalette` adding additional spaces between characters in the autocomplete suggestion list
• Ensure that the new sprotty protocol is used consistently over the deprecated old class-based action API
• Bugfixes for the edge intersection detection
• Add the possibility to run ELK layouts in a separate Java process
• Improve Projections feature