Improve filename parser
Improve filename parser

Only accept filenames if the whole filename gets matched by the regular expression
and show a warning for unmatched files.

freifunk-bielefeld/firmware-wizard,freifunk-darmstadt/gluon-firmware-wizard,freifunk-darmstadt/gluon-firmware-wizard,codedust/gluon-firmware-wizard,freifunk-bielefeld/firmware-wizard,codedust/gluon-firmware-wizard,freifunk-darmstadt/gluon-firmware-wizard,codedust/gluon-firmware-wizard