[plugins] director: added initial HTB-like queuing discipline support.

support.
flow.vim: adapted to director plugin changes
[plugins] director: working around "private member not used" Clang compiler warning
[plugins] director: added missing content-type response header to haproxy?monitor stats
[plugins] director: fixed bug in CSV output only showing pxname on first backend.
[base] Buffer: added `bool operator==(Pod, BufferBase)`
[base] Url: fixed bug in parseQuery() when passing ranges that do NOT end with EOS implicitely and avoid using std::string as it calls strlen(), but our buffer potentially doesn't end with EOS either.
[base] TokenShaper: overall API improvements.
[tests] added basic Tokenizer test
[plugins] director: some debug prints wrt HttpHealthMonitor
[plugins] director: code cleanup in RequestNotes.h
[plugins] director: implements JSON API for the new Request Shaping feature.