Snapshot integration

[ginesdt]

Summary

Integration as described in #116
With this commit, a new district is no longer linked to a new aragon-id, but it is now a 2-step process where firstly the district is created, and then it is linked to Snapshot.
Thus, when creating a district, both the UI and District smart-contract has been modified to check the current user is the owner of the ens-name to be associated to the district. Once created, a new button appears to create the Snapshot, which will perform all the process required to create the snapshot (create and upload snapshot description to ipfs, update ens record, etc.).
Note: even though not explicitly said in the requirements, I added a check both in the UI and in the smart-contract side to avoid creating a district if the ens name is already linked to a snapshot (we can easily remove this checks if not actually needed).
Unit tests have been also adjusted.

Review notes

Testing notes

[madvas]

Hi, thanks for well made PRs. We might be interested in further collaboration with you, if you are as well, please drop us an email at [email protected]