[backend] print repo error message
[backend] use get_build instead of get_deps when expanding kiwi images

get_deps filters away preinstalls and support packages, which may
break the build...
[webui] Show request priorities
[webui] Get rid of /user/requests/ in html
[backend] do not come with a download_url in backend config anymore by default

we have by default a different config in /configuration which breaks test suite
[api] just switch order of migration steps

It is one big transaction and people are confused not to see
changes, when the warning of not converted entries pops up in the middle.
[doc] explain priority meanings
[backend] publish all install.tbz and tgz kiwi images
[api][webui] use download url's as reported by the backend

Otherwise the download might break on special mappings
[backend] use new published path code also for productrepositories call

bs_admin has no support anymore for product repository path, because a
pure offline resolution is not possible anymore.