Add support for printing owner of file in announce

When a mkv or mp4 file has been uploaded it's now possible to also
print who uploaded the file (so you know whom to yell at).
Fix irc trigger for dirs with multiple mkv/mp4 files

When the irc triggers were used for a dir that contained multiple mkv
or mp4 files it would not work as findM??InRelease function returned
a nested instead of a flat list.
Remove debug print from mp4size