[PATCH 0 of 6 DEFAULT] remove: support explicit paths in subrepos

[David M. Carr]

In the past several months, there's been a lot of discussion about subrepos,
difficulties in using them today, and the path forward.  Several times, Matt
Mackall has requested that someone assemble a patches to have "hg add",
"hg forget", and "hg remove" transparently handle adding explicit files in
subrepos.  I've submitted previous patches for add and forget; this series is
for remove.