manifest: change terminology for storage in context classes
Storage may not be backed by revlogs. So it is wrong to refer
to storage as "revlog" or use abbreviations like "rl."
This commit replaces revlog terminology in manifest context classes
and starts referring to things as "store" or "storage."
Differential Revision: https://phab.mercurial-scm.org/D4389
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.