- refactor types to create submodule
- Spectra is now a class instead of a simple list from XasObject
- Spectra contains data which is a numpy ndarray of Spectrum. This was it is simpler
to reshape it andd should offer some flexibility for the futures.
- this is the main PR but several smaller one are expected to come for cleaning...

update xas input

Closes #29, #20, and #28

See merge request workflow/est!31

Avoid creating DataUrl with empty path. Return None instead

Fix exec pre 0 3

See merge request workflow/est!30

This reverts commit 9dd8869d.

project update for 0.3

Closes #26, #16, and #17

See merge request workflow/est!29