bundle-ng: unify _changegroup and _changegroupsubset
Refactor the two changegroup generation interface to share as much code as
possible.
bundle-ng: move gengroup into bundler, pass repo object to bundler
No semantic changes made.
bundle-ng: move bundler creation up in the stack
Create a simple start() method to pass the lookup function until bundler
becomes smarter and gets a repo object.
Since we now create the bundler for the whole lifetime, we need to pass it
down to revlog methods.
i18n: fix untranslated prompts with translated responses (
issue3936)