wireprotoserver: rename abstractserverproto and improve docstring
The docstring isn't completely accurate for the current state
of the world. But it does describe the direction future patches
will be taking things.
Differential Revision: https://phab.mercurial-scm.org/D2065
pager.pager=p0 # $TESTTMP/sysrc:4
ui.editor=e1 # $TESTTMP/userrc:2
pager.pager=p2 # $PAGER
ui.editor=e1 # $TESTTMP/userrc:2