contrib: Make remotes2config.sh script more robust

contrib: Make remotes2config.sh script more robust

The remotes2config.sh script replaced all 'unsafe' characters in repo
name with '.'; include '-' in the 'safe' characters set (the set is
probably even larger).

Script required also space after "URL:", "Push:" and "Pull:" in
remotes file. This for example made the following remote
  URL: git://git.kernel.org/pub/scm/git/git.git
  Pull: refs/heads/master:refs/heads/origin
  Pull:+refs/heads/pu:refs/heads/pu
miss 'pu' branch (forced branch) in config file after conversion.
Allow for any number of whitespace after "URL:", "Push:", "Pull:".

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>