Improvements

Python package structure

1. Add unitary tests

2. Add an abstract class for the Meta classes (example : GetBaseMeta)

   There are many common attributes between the meta classes. This improvement could make a lighter code and make easier the maintenance.

Non-treated cases

Some combinations aren’t yet treated by this tool. These cases should be treated. Here is a recap of the treated and non-treated cases:

	truncated_swath	swath	daily_regular_grid	model
truncated_swath	listing=True, product_generation=True	listing=True, product_generation=False	listing=True, product_generation=True	listing=True, product_generation=True
swath	listing=True, product_generation=False	listing=False, product_generation=False	listing=False, product_generation=False	listing=True, product_generation=False
daily_regular_grid	listing=True, product_generation=True	listing=False, product_generation=False	listing=False, product_generation=False	listing=True, product_generation=False
model	listing=True, product_generation=True	listing=True, product_generation=False	listing=True, product_generation=False	listing=True, product_generation=False