GitLab

Fixed issue with restricted search and mixed material/calculation queries, added initial regtest for complex query, updated GUI version.

- Move elasticsearch to test_get_dataset so test_mapping
  can be tested locally without the need for elasticsearch

Renamed to page_size, page_after_value, next_page_after_value, next_page_url. Added prev_page_url and first_page_url

Harmonized behaviour of after/next_after, improved doc, and moved DatasetPagination from models.py to datasets.py