Correctly update scala version in MANIFEST templates
Update only scala-compiler if SDT >= 4.0
Update the generate ecosystem logic for 4.0.0

With Scala IDE build >= 4.0.0-rc1, a plugin is compatible if the Scala
library range is the same, the sdt core range contains the sdt version
and the Scala compiler version match strictly, if the dependency exists.
Bumps the version number

None trivial changes made for Scala IDE 4.0.0
Prepare for 0.5.0 release
Prepare for next dev cycle
Fixes typo in luna repo URL
Prepare for release 0.5.1