better tracing for pyco

[koo5]

currently, pyco dumps the whole proof tree at every step, this is slow.
support for emitting incremental changes needs to be added:
add_state id with parent id
remove_state id

additionally, generating text describing bnodes is slow, it should be moved to the trace viewer. For that end,
pyco needs to output all changes to locals.

the frontend needs to use rdf.js to load up the kbdbg rules description, as emitted by pyco at startup

the frontend also needs means to go forward and backward at least between the (numbered) trace files.
at the beginning of each trace file can be a full dump.