More linting

- better name for scala installs
- equals for ScalaInstallation
- formatting, error messages typos
- no Default & apply for Scala Installations
- legacy bundles have a better tag
- sparser labels for Scala isntallations
- cleaner, unified names for installs in dialogs
- don't modify the existing install in case of refused solution
Put notifier updates on the Display Thread

Also corrects initialize semantics change in compiler settings upon
background change
Only correct a cross-compiled classpath Once
DO NOT trigger a classpath check at the end of setDesiredXXX

- the listener will pick up soon enough on that
- also, better error messages w/projcet name

Also, more informative error markers.