Whoops, also install educe.{rst_dt,pdtb} subpkgs
pdtb: ExplicitRelation s/connective/connhead/

I worry that connective would be misleading (connective text
is the selection text); head should just be a substring
pdtb: Fix and try to notice some type errors

*SIGH* Dynamic typing
Kill dead import in tests
educe.pdtb.xml_ : conversions w adhoc xml format
Fix bug in educe.util.mk_interesting

It was requiring that all fields be defined
Move indentxml to educe.internalutil
Stop cargo culting obsolete ElementTree import
pdtb: include first two digits of doc in path
educe.pdtb.xml_: export some high-level functions
docs for some new modules
pdtb files are in iso8859(-1?)
pdtb-util swiss-army-knife (has xml converter)