Slightly refactor addresee detection

The hope is to be able to run it from a different pipeline
Tighten up addressee prediction a bit

Don't predict addresee if followed by a verb or
preceeded by a preposition
ENH: educe.stac.annotation.{set_,}addressee

Functions to get and set the addressee feature for an
edu annotation
Merge branch 'master' into rst-split-feat-extraction
Merge branch 'rst-split-feat-extraction' into rst-dep-fake-root