Modified travis to not compile plugins

Thanks to Haruna.

Signed-off-by: shennetsind <ind@henn.et>
pc_groups interfaced

The last file without a interface is now no more (date.h doesn't count :P).
Modified the way permissions are stored in order to enable plugins to be able to create permissions ( pcg->add_permission("name") [returns permission key] ).
Special Thanks to Haruna!
Closes #121

Signed-off-by: shennetsind <ind@henn.et>
Merge branch 'master' of https://github.com/HerculesWS/Hercules