Move common functionality between labeled collectors out of
ValueCollector and into a new LabeledCollector class, and use this as
the basis for implementing a Histogram collector.
Split up codebase into the packages @clsterio/lib, @clusterio/master,
@clusterio/slave, and @clusterio/ctl using lerna to manage them. This
will allow deployment to use only the parts needed reducing install
size, and better separate the code into shared library, master, slave
and control.