afew: rewrite expression

it's an application, not a python module

Also, remove name attribute.
Build with python 3 by default.

afew: make setuptools_scm a buildInput

afew: don't set SETUPTOOLS_SCM_PRETEND_VERSION anymore

we fetch from pypi, with version info properly set, so this shouldn't be
an issue.

afew: set license

afew: add notmuch binary to PATH

it seems afew calls "notmuch new" in MailMover.py

afew: don't set LD_LIBRARY_PATH

the library is already hardcoded pythonPackages.notmuch's globals.py