macros only require scala-reflect, not scala-compiler
add sbt-about-plugins

add sbt-about-plugins
Docs: pass build values to sphinx/conf.py via environment variables to reduce duplication.
Docs: Add cleanupCommands to howto
Docs: remove stray line in Howto/scala
Docs: Add scaladoc/javadoc howto
Docs: fix problem with title being hidden