store: rename "openertype" argument to "vfstype"

localrepo: use "vfs" constructor instead of "opener" one This patch also changes initialization order of "*opener" and "*vfs" fields: first, "*vfs" fields are initialized , and then, "*opener" ones are initialized.

scmutil: rename classes from "opener" to "vfs" For backwards compatibility, aliases for the old names are added, except for "abstractopener", "statichttpopener" and "_fncacheopener", because these are not used in Mercurial core implementation after this patch. "_fncacheopener" was only referred in "fncachestore" constructor, so this patch also renames from "_fncacheopener" to "_fncachevfs" there.