Addded sbt-extra and removed launcher

Great comment on reddit (by predef) to remove the launcher and instead
add an entry in my build.properties file and switch to using the sbt-extra
script. So, since it was a great idea I did exactly that. :-)
removed sbt-idea from plugins.sbt

I realize now that I should be using a global plugin for this instead
Merge branch 'sbt-extra'