Update dir-spec.txt with microdesc, consensus-flavor info
The microdescriptor and consensus flavor improvements are live in anything running the 0.2.3.0.x master code: they should get into the doc-spec.txt file.
This will involve extracting stuff from proposals 158 and 162 and comparing them against to code to make sure I didn't deviate from the proposals (and if I did, whether I was right to do so).