Code style.

- Added Javadoc;
- changed style of the code blocks to a more clear, with more spaces, style;
- added comments;
- added spaces between the methods;
- removed useless checks (like if(var == true) {}).
Added visibility on all methods.
Moved the commands to an external command executor.
A subcommand is executed by a method in the external class.
Added personalized error messages for unauthorized users.
Fixed a bug when the console executes /spec on or /spec off (ClassCastException)
Fixed some typos.
(Minor, this was not a bug.)
Internal variables are protected, instead of public.
Added error messages for unknown sub-sub-commands.
Merge pull request #9 from AmauryCarrade/clean

Enhancements on the source code and the command manager