Removed old PE support code
Removed old PE support code

The nes PE support is now the default one, since it's the only one which permit PE 1+ worlds to be edited.

The lines:

```
loadNBTCompoundList
newPocketSupport
levelDBPy
```

Can be removed from the `new_features.def` file, and the CLI switch `--new-features` is no more needed.

(Referencing #805, #803, #801, #779, #676, #671.)

fhfuih/MCEdit-Unified,fhfuih/MCEdit-Unified,Khroki/MCEdit-Unified,Khroki/MCEdit-Unified,Khroki/MCEdit-Unified,fhfuih/MCEdit-Unified