* Simple settings interface implemented in in apsg.core.seetings dictionary.
To change settings use:
from apsg.core import settings
setting['name']=value
* `notation` setting with values `dd` or `rhr` control how azimuth argument of
Fol is represented.
* `vec2dd` setting with values `True` or `False` control how `Vec3` is
represented.
* Vec3 could be instantiated by one arument (vector like), 2 arguments
(azimuth, inclination) or 3 arguments (azimuth, inclination, magnitude).
* Group and FaultSet can return array or list of user-defined attributes of
all elements