This change adds the possibility to exclude certain
protocols to be entered in MirrorManager. The default
value in the configuration file of
MM_PROTOCOL_REGEX = '^(?!ftp)(.*)$'
will prohibit that FTP based URLs are entered at all.
The goal (as discussed in #99) is to remove FTP URLs from Fedora's
Signed-off-by: Adrian Reber <email@example.com>