Migrate to oslo.middleware

Synced middleware module from incubator instead of removing it
completely. This is needed for grenade and to keep backwards
compatibility with existing installations with old api-paste.ini.

'log' module is updated as a dependency for middleware module.

'versionutils' are added as a new dependency for middleware module.

Closes-Bug: #1371701
Change-Id: Ib1c3161ccc98642091134f2285fed7c90244e600
Co-Authored-By: Ihar Hrachyshka <ihrachys@redhat.com>
Migrate to oslo.i18n

Mostly trivial import changes.

- oslo.i18n no longer provide install() method to inject _() into
  globals(), so removed all calls to it;
- removed Babel from dependencies (it will now be grabbed by oslo.i18n);
- updated tox.ini to ignore import violations for oslo.i18n.

Change-Id: I6623d551f512fb7fe9bf35ee734ed6d4c6cbc287
Merge "Migrate to oslo.middleware"
Merge "Migrate to oslo.i18n"