Moved block and item creation from init to preinit; Fixed proxy system

I tried to build and use the version from `master` branch and encountered a crash, which was caused by attempting to register a recipe which uses Saw before the Saw is actually constructed.

According to FML's Javadoc, PreInitialization is a valid place to construct and register items and blocks.

Then I encountered another issue.
Let's look at CoreClientProxy class. It inherits CoreProxy.
Let's look at ClientProxy class. It inherits CommonProxy and calls methods from superclass.

As a result, there's a problem: proxy methods may be called twice. I hope you see the problem now because I have trouble trying to explain what's wrong.