Since rationals aren't a known Qt format, the QVariant container can't
automatically convert them to and from strings (for XML serialization). We have
to hijack these functions and do the conversion manually for those types.
Also moved the block name type to a node input, which means it's serialized
and copied by default (I'm not sure why it wasn't already like this).
Transitions are nodes but have a few parameters that are programmatic and always
required. This lets people write external code for transitions as well.
itsmattkc