Node::load_data: trace when data is dropped or skipped
cme: force write back when called with 'migrate' command...

... so file is written back even if no semantic change was done. I.e.
unused elements are dropped.
cme: updated pod doc
cme: force write back if -force option is used
Added JSON backend
test JSON backend
Updated pod of Config::Model
specified module version dependency in "use" lines
dist.ini: use auto prereqs
dist.ini: use auto prereq
dist.ini: use pod weaver
Config::Model: generated doc is compatible with Pod::Weaver
adapted pod to pod::weaver. moved pod at end, deleted trailing spaces. no other changes