Develop a new major version

[amercader]

ckanext-spatial is an old extension and hasn't had a big refactoring in a long while. Postgis and other python requirements make it difficult to install and deploy. In addition, the spatial search capabilities in Solr have evolved significantly since the current implementation and both indexing and querying can be greatly simplified in ckanext-spatial.

The main areas of work will be:

• Dropping PostGIS requirement (#195 ). Support only Solr-based search (the PostGIS one is not suitable for production anyway)
• Refactor search logic. Use modern Solr fields to support the existing backend modes (solr for bboxes and solr-spatial-field for polygons, points, etc), they can be probably merged into a single implementation. Write actual Solr based tests. See #291 This work could be tagged as v2.0.0, and ideally will only target CKAN 2.9+ in Python 3, although we can re-assess this when we know the scope of the changes

cc @avdata99

[avdata99]

@amercader I think #289 could be part of this mayor change. I assume you want to take care of this, but let me know if I have to do any of the work. Maybe start building version 2.0.0 for Python 3.