Move orhelper logger out of file scope

[Jashaszun]

Since the orhelper logger is created in the file scope of _orhelper.py, it is created when orhelper is imported. This means that to assign settings to that logger, clients have to import logging themselves, get the logger that orhelper will be assigned with logging.getLogger('orhelper._orhelper'), assign settings, and then finally import orhelper. This is quite ugly in client code and it would be much nicer if the logger was created after import, i.e. in the OpenRocketInstance constructor.

[Jashaszun]

Never mind, you can actually assign orhelper logger settings after import.