Lots of code refactoring done. See desc for details.

- Renamed and reorganized some classes and packets
- Removed Axe achievement in TickHandler
--> Was causing a crash on dedicated servers and is not worth working
around atm
- Removed tons of redundant or unnecessary code
- Moved Item and Block Registration from Main class to others
- Created a basic Machine TE which can easily be extended to create
different kinds of Machines
- Added an Interface for MultiBlockStructures to ensure that all needed
fields and methods get implemented.
--> Gonna do this for TE of Multiblocks too
- Added a first version of the Ore Mill