set forkCount as a property

  * To play on the safe side use forkCount=1 as default.  This can be changed
    via command line, e.g. `-DforkCount=1.5C`.

  * This commit restores lost commit
    (383bd8ee0ee4168ff1d69864a860971ec1c1726f) when renaming folders

Conflicts:
	parent/pom.xml