File blocking refactor

[brachy84]

The current system is flawed:

• changing the security manager before and after each script and closure execution
• sometimes errors on things reading files from gradle cache

This removes the sketchy security manager. Instead we

• ban java.io, java.nio.file and java.nio.channels
• create a wrapper class for java.io.File
• add most convenience methods from groovy to it
• redirect File() ctor to GroovyFile() ctor (the wrapper).

The file wrapper resolves the given path to minecraft home path and then checks if the file really is in minecraft home.
Then on each read/write method we check accessability and crash if we cant access.
Just creating the file will not error. Only until you want to read or write the file. Users can check accessibility with .isAccessible() or canRead()/canWrite(). exists() is always safe to call and ignores accessibility.

With this we make file blocking future proof (since modern java will remove security manager) without any performance concerns.
Of course there are still ways to bypass this, but being 100% save is not possible anyways.