feat: add `get_pkg_version()` convenience function

this is only needed until we can require python 3.8+

Bump version for wuttjamaican lib

need the latest

Whoops can't remove subcommand entry points just yet

need these just in case we have to revert in emergency etc.

Add all `rattail-cli` commands using typer

these will "soon" be wired up as `rattail` but one thing at a time

Add basic support for `typer` command system

only using this for derivative projects so far..proper rattail
commands will be migrated last probably

Require latest wuttjamaican

since tox doesn't want to fetch latest available, must force it here

Bump requirement for wuttjamaican

to ensure generic handler class exists

Use upstream subcommand for `rattail date-organize`

mostly to confirm that upstream subcommands may be used as-is with
main rattail command

Move core command logic to `rattail.commands.base`

deprecate `rattail.commands.core` to align with upstream convention

Refactor the main Command class to use more upstream logic

in particular the usage help text is now auto-generated to include all
main command args

Add proper wutta wrapper for `make_config()`

fingers crossed we didn't break anything!

Bump version dependency for wuttjamaican

will we need to keep doing this..?

Make explicit which python versions are supported

as of writing, all of 3.6 thru 3.11

in practice i don't know of anyone running 3.7 so that may get dropped
sooner than later. unfortunately there are still a couple of 3.6 apps
but after those are upgraded probably the minimum supported version
will become 3.8

Incorporate the WuttJamaican package

- our AppHandler is now based on that one
- our Config *may* be based on it, if so configured

at some point our Config will "always" be based on WuttaConfig but we
need to test a bit more first

Add `rattail auto-receive` cmd, as versioning workaround

when doing "auto-receive" for a receiving batch, need to disable
versioning as the process is too slow with it enabled

this also tweaks a couple of things that came up for KeHE

Tweak `upload_dir` option in `setup.cfg`, per warning

not sure this is actually being used anyway..? need to revisit

Remove some config for nosetests

buildbot is using only pytest now, but will leave nose in the test
dependencies until other packages are updated, e.g. tailbone

Add new bulk PostgreSQL and Rattail->Rattail importers

Plus tests, sort of..plenty of stubs in here still.

Add docs to `release` task.

Hopefully it works, right now getting a 503 from PyPI about it...

Prepare for tests.

This doesn't add any actual tests but it should pave the way for that. Tests
may be run like so:

{{{
python setup.py nosetests --with-coverage
}}}

Removed `setup.cfg` file.

The `tag_build` setting was not doing us any favors.