Updated submodules to the new repository URLs
Changed URLs to be relative in .gitmodules
Remove old TODO file, using trac tickets instead

- #2104 (Check: Bytes sent and time listening might be broken?)
- #2105 (Make config option (-c) optional?)
- #2106 (Pull vorbis comments (metadata) and send to stats)
- #2107 (Provide a way for YP Dirs to check streams)
- #1944 (Rework STATS interface)
- W3C Extended Logging was never requested by someone
- Sending intros is already possible
- #2108 (Registrable URL handlers in connection.c instead of hardcoded list)
- #2109 (Abstract admin functionality to set of commands and handlers)
- #2110 (Timer-based functionalities should use single timer thread)
- #2111 (Race condition in fserv.c?)
- #2112 (Locks on avl client_trees needed?)
Updated README, renamed it so that it is parsed as markdown