Importing the library without a world open should behave more clearly

[caranha]

Feature branch: None

If you import sub-modules from the library (for example, GEO) without a minecraft world open, a large scary error message shows.

Either you should be amble to import sub-modules without a world running, or if that is impossible, a better error message (i.e "Don't forget to open the minecraft world before loading this module!") should be displayed (or maybe an appropriate error should be thrown?)

[avdstaaij]

Moved to avdstaaij/gdpc#39