Added support for ASK and DESCRIBE queries in the sparqlwrapper backend

[jesper-friis]

Description

Added support for ASK and DESCRIBE queries in the sparqlwrapper backend.

General useful to have and needed by draft PR #361.

Type of change

• Bug fix and code cleanup
• New feature
• Documentation update
• Testing

Checklist for the reviewer

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?
• Is the code properly tested?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.01%. Comparing base (4352479) to head (8a5f050).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #364      +/-   ##
==========================================
+ Coverage   77.96%   78.01%   +0.04%     
==========================================
  Files          25       25              
  Lines        2914     2929      +15     
==========================================
+ Hits         2272     2285      +13     
- Misses        642      644       +2     

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