SBT, Maven, Gradle: merge module settings
(cherry picked from commit 2324f15)
ScalaCompilerSettings: parse compound -language:... options
(cherry picked from commit 9662f33)
JPS: don't show "No Scala SDK" warning for SBT "build" modules
(cherry picked from commit 788d46b)
JPS: show explicit error when Scala compiler JARs are absent
(cherry picked from commit 7883d15)
Don't hide non-existent files in path editors
(cherry picked from commit 77a23fb)