Merge pull request #24 from picturae/17295

Refactor import method. Implement concept schemes purge option. refs #17295
Merge pull request #25 from picturae/17544

Add additional check for unique notation. refs #17544
Refactor how the external relations are fetched. refs #18153
Fix in solr client. refs #18153
More refactoring of relations fetching. refs #18153
More refactoring of relations fetching. refs #18153
Do not fetch schemes one by one when prepearing the edit form. refs #18153
Check for unique notation only in the scope of the tenant. refs #18153
Check for empty relations which somehow exist if editing concept with no relations. refs #18153
Merge pull request #37 from picturae/18153

Refactor and optimize the way the external and internal relations are fetched. refs #18153