Scala version detection changes
Scala version detection changes

* Deprecated version_str
* Reimplemented Scala.version to give preference to scala.version, then read library.properties (avoiding RJB)
* Altered compiler precedence to prefer scala.version over SCALA_HOME
* Use SCALA_HOME when scala.version points to the same version (to allow FSC)

git-svn-id: d8f3215415546ce936cf3b822120ca56e5ebeaa0@930764 13f79535-47bb-0310-9956-ffa450edef68

jpcaruana/buildr,jpcaruana/buildr,stewi2/buildr,stewi2/buildr,stewi2/buildr,liamchristopher/buildr,stewi2/buildr,apache/buildr,apache/buildr,apache/buildr,liamchristopher/buildr,liamchristopher/buildr,liamchristopher/buildr,jpcaruana/buildr,apache/buildr,jpcaruana/buildr