introducing a RootCollector. Note that the internal node
methods _fromtrail and _totrail are shifted to the still internal
config._rootcol.fromtrail/totrail
--HG--
branch : trunk
* separate all tests from plugins
* simplify implicit inclusion of plugins under test
* have test_initpkg perform direct checks instead of yielding tests
* fix example tests for 3k
--HG--
branch : trunk