MailMover: many fixes
Previously, MailMover didn't properly preserve flags when renaming files, and
moved all mail to `cur`. This was fixed. Also, MailMover gained a test suite.
New filters: PropagateTags[ByRegex]InThreadFilter
These filters allow propagating tags set to a message to the whole thread.
New command line argument: --notmuch-args= in move mode
In move mode, afew calls `notmuch new` after moving mails around. This
prevents `afew -m` from being used in a pre-new hook in `notmuch`.
Now it's possible to specify notmuch args, so something like `afew -m
--notmuch-args=--no-hooks` can live happily in a pre-new hook.
Python 3.4 and 3.5 support dropped
afew stopped supporting the older python versions 3.4 and 3.5, and removed
some more Python 2 compatibility code. (`from __future__ import …`, utf-8
headers, relative imports, …)
906dccf595