Moved TRLimitFly into TRThread.

- Feature is currently not working and is disabled by default.
Mayor SafeZones overhaul.

- Added a new config file: SafeZones.config.yml
- Added alot of information about safezones and their settings in the
SafeZones config.
- Implemented 4 different modes for GriefPrevention SafeZones. (This has
not been changed everywhere.)
- GriefPrevention SafeZones now also support the support that only
WorldGuard SafeZones used to have: DechargeEE, DisableEntities, etc.
- Cleaned up code around SafeZones.
- Improved code around SafeZones.

Removed String == "" and String != "" all over the project as Strings
should be compared with .equals("");