Handle Alpine release in pkgkit

Actually fix old package removal

pkgkit: fix removal of previous version

Improve hg version detection

Add hg support to `pkgkit pkgver`

Update pkgrel after updating pkgver

Add pkgver function

Really fix pkgrel handling for really real

Fix pkgrel logic

Add some additioanl verbosity to pkgkit

Move abuild checksum to after pkgver is set

Fix pkgkit build -r/-u inconsistency

Add pkgkit helper binary