Suggestion: Create Interface for MachineBaseBlockEntity

[ghost]

We are using RebornCore for our new mod ChaosStorage. It has proven to be very useful because it solves a lot of common problems, but during development we ran into the limitation that many helpers expect that the MachineBaseBlockEntity class is used.

In our case this requires us to decide between being able to share many common Overrides for BlockEntity classes, which have to be in a class that extends BlockEntity, and using most of the RebornCore helpers.

My proposal is to add a new Interface IMachineBaseBlockEntity or similar that has all the method heads that are accessed by the RebornCore helpers. For mods that use the MachineBaseBlockEntity included in RebornCore nothing would change, but other mods could have their own class and still use the helpers.

If this sounds ok to you I would prepare a pull request to implement this.