Fix all pkgcheck errors

[kir68k]

Annoyed at myself >.>

References: https://github.com/kir68k/xira/issues/13

This adds:

• metadata.xml to all packages, like it should've been on day 1
• the metadata/md5-cache directory
• fixes unacceptable warnings for "profiles" and sets
• fixes all pkgcheck failures/errors

[kir68k]

Sighhh, locally this works, alright then...