Fix: make limits/... work with numpy arrays

Passing in a numpy array instead of a list fails tests like `if values:`
as numpy arrays raise a Exception: "ValueError: The truth value of an
array with more than one element is ambiguous. Use a.any() or a.all()"

Closes: #333
Fix: export all scales
Fix: let ticklabels also be arrays...
Cleanup not needed imports/exports for scales
Merge pull request #344 from JanSchulz/fix_333

Fixes for inputs being numpy arrays and cleanup scale imports/exports