brother_ql fixes upon fixes

Will it work this time?

brother_ql real fix

This release adds the git command to the image (at least for building) so the necessary pull request can be fetched from the github repository.

fix brother_ql

This release uses a pull request for brother_ql, to deal with changes in python pillow module. Fixes infrastructure#177

Improved release instructions

make release instructions more explicit.

p2k16-label docker image

This release has the following improvement: the python script now uses the dns name of the printer, not the ip address.

test release for p2k16-label docker image

try to use correct yaml syntax

test release for p2k16-label docker image

try to add more debug info.

test release for p2k16-label docker image

add more debug info.

test release for p2k16-label docker image

now with syntax not failing, do I get debug output?

test release for p2k16-label docker image

add some debug info, maybe I can spot the problem