Tear out incoming/outgoing functionality

This stuff is the most brittle part of hg-prompt, and I never use it.
I don't have the will to maintain it as Mercurial constantly breaks
backwards compatibility in their plugin API.  At this point I regret
ever writing a Mercurial extension.  I'm sick of the Hamster Wheel
of Backwards Incompatibility eating an hour of my life every time I
stupidly decide to upgrade my software.

fix error with hg versions <4.3 (regression from commit:4dddc56)

Use @registrar.command where available (hg 3.7+).

Merge.

Fix example of HGRC template in help output

Command line overwrites format string from HGRC

Also extends help to mention hgrc setting.

Add test for reading format string from HGRC

Use format string from HGRC if available

This allows repository specific prompts (e.g. no status in large repos
or no incoming/outgoing on repos where the remote communication is too
slow).

Merge.

Backout the daemon stuff

I fixed my deployed `hg-prompt` thinking I had done it
in the version I pushed to bitbucket. I only noticed it
because I had to reinstall. :/

o Daemonized the hg incoming/outgoing calls to increase responsiveness;
o Added zero option to incoming and outgoing that will expand 0 counts.

Fixed `hg help prompt-keywords` to display the help text

Clean up error message

Merge.

add support for non-default remote with incoming/outgoing

Merged in sietsebb/hg-prompt (pull request #13)

Also hide ^ marker when on a non-tip head

Also hide ^ marker when on a non-tip head

Use @cmdutil.command decorator to define command table.

It's been available for 5 years (since Mercurial 1.9), and Mercurial 3.8
deprecates the use of hand-built command tables as of 38dc3f28f478.

Fix bookmark output on Mercurial 3.5.

Mercurial 3.5 renamed the `repo._bookmarkcurrent` attribute to
`_activebookmark`.