feat(structural) : import of structural data to database

This MR is about #305 (closed), and goes with new xplordb update (0.13.4).

What's new :

• import of POLAR data
• import of SPHERICAL data

Polar data is similar to numerical data, but spherical ones need some UI change :

• a new section in assay importer to map dip, azimuth, type and polarity

Database side, polar data is stored :

• as float in spatialite
• as assay.azimuth domain in xplordb

Spherical objects (plane or line) are stored in a single column as :

• JSON-like text in spatialite
• assay.spherical_data composite type in xplordb