Notable changes:

* New `source` and `artifact` command groups
* Man pages corresponding to obsolete commands, that were marked as
  hidden in Click, have now been removed.

Fixes #881.

Due to an upstream click_man issue:
https://github.com/click-contrib/click-man/issues/10
generating the man pages with our current setup.py only generates
a man page for bst-artifact-server, our first entry point.
I then had to remove this entry point from setup.py and regenerate to
obtain man pages for the commands in cli.py

It seems that the regenerated man pages haven't been committed for some
time. Add them all in one lump now.

Had to manually strip the version number from the generated files.

Had to manually fix the NAME field of bst.1 to not be 'bst - None'.

Oddly had to invoke click-man directly in order to get the changes to
be applied, the usual setup.py route mentioned in contributing.rst
didn't work.

Eyeballed the result of invoking man on each of the commands, seems
good.

One of the tests added is configured to be skipped for now, as dumping
binary data is causing a bad descriptor exception when using the pytest
capture module.

Closes #263.

This needed an update at least for the deprecation
of `bst build --track-save`