Fix for respawning + /respawn command

- Player is automatically respawned when logging in
- Added /respawn command (MC 1.7 does not fail to respawn)
- Cleaned MCC command handling code, /exec is now /script
Scripting bot : automatically find script file

- Automatically look for script file in config/ and scripts/ folders
- Automacically try to add '.txt' extension to the script filename
- Eg "/script testscript" properly loads "config/testscript.txt" script