[Scala] remove external tools excludes.

Remove excludes for SBT, Eclipse and ENSIME. They'll be added to appropriate
Global/ gitignore files.

Scala.gitignore

 *.class
 *.log
-
-# sbt specific
-.cache
-.history
-.lib/
-dist/*
-target/
-lib_managed/
-src_managed/
-project/boot/
-project/plugins/project/
-
-# Scala-IDE specific
-.ensime
-.ensime_cache/
-.scala_dependencies
-.worksheet
-
-# ENSIME specific
-.ensime_cache/
-.ensime