Add set and remove alias functionality

[alejgh]

Closes #18

[codecov]

Codecov Report

Merging #30 into master will increase coverage by 0.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #30      +/-   ##
==========================================
+ Coverage   95.10%   95.35%   +0.25%     
==========================================
  Files          14       14              
  Lines         469      494      +25     
==========================================
+ Hits          446      471      +25     
  Misses         23       23              

Impacted Files	Coverage Δ
hercules_sync/triplestore/wikibase_adapter.py	98.27% <100.00%> (+0.44%)	⬆️
hercules_sync/util/uri_constants.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 138a6a0...b4c4c92. Read the comment docs.

[alejgh]

There is currently a problem when removing the last alias for a language of the entity. For example, if you have as aliases of Person ['subject', 'individual'], removing one of them works, but if you want to remove all the current aliases of Person, the operation is not made.

This is a bug of the wbeditentity API method: https://phabricator.wikimedia.org/T203337
That was resolved and should be working correctly from wmf 1.35.0 onwards. I will create a new issue to update to 1.35.0 whenever it is available in wikibase-docker, and check if this bug is fixed. For the moment, I will close this issue.