Transition from migrate to alembic

Toolkit for smooth transitioning from migrate tool to alembic.
Check README for some description

POC: Integration with nova-manage https://review.openstack.org/#/c/60517/

Blueprint: oslo-migration-toolkit
Change-Id: Icfa7d8736a84da1a4890eb417d48bab4c73e1f89
Backport 'ident' from python 3.3 for Oslo's SysLogHandler

To honor RFC5424 add use_syslog_rfc_format config option
(default False, would be deprecated in J after existing
syslog format deprecation) which adds APP-NAME to syslog message
before MSG part to reflect application or service name.
Usable only with use_syslog, otherwise ignored.

During J, the default logging format for syslog should be changed
to always provide APP-NAME, thus use_syslog_rfc_format could be
deprecated in J as well.

DocImpact
Closes-bug: #904307

Change-Id: I3815e6dc47e206e15f9da90ebbba5ca00c3ae641
Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Ported hooks

Decorator and config option definitions for adding custom code (hooks)
around callables.

For example, we can use hooks to easily add specific request headers in
different clients without changing common code.

Change-Id: Ic635d3f6ce32544dbd739515c26b7984e055fb1a
Merge "Ported hooks"
Merge "Transition from migrate to alembic"
Merge "Backport 'ident' from python 3.3 for Oslo's SysLogHandler"