Add scala 2.10.0 as a cross build plus (and some minor changes)

    * Upgraded sbt to 0.12.1 because starting with scala 2.10.0, dependencies do not build for the minor bug fix version.
    Meaning, the dependency for lift webkit for scala 2.10 is
    
    net/liftweb/lift-webkit_2.10/2.5-M4/  (note that it is not 2.10.0 ) sbt 0.11.x does not know how to handle this, but sbt 0.12 does
    
    * The web plugin version does not map to sbt version any more, so we are explicit about which one to use
    * Added scala 2.10.0 as a cross build version of scala