Cleanup layout of repository:
- move web content to separate subdirectory www/ and make contest a
  symlink to currently active contest with config/common data.
- move misc. auxiliary scripts to subdir.
Unset executable bit from team logos.
Add index page redirecting to iCAT overview.
Move configuration data to YAML config file instead of in PHP code.
Also fixes some uncorrected locations icpc/ in previous commit.
Merge git homedirs start script into the common script.