Create update procedure for v1.5

[marcelstanley]

📚 Context

Release v1.5 comes with a breaking change in the way epochs are calculated when compared to any previous v1.x release.

Such change objectively fixes #432 and, in doing so, requires that existing applications upgrade their version of the node and their instances of the History contract to have their history rewritten.

✔️ Solution

Define and test all steps required for upgrading an application from v1.4 to v1.5 if needed.

Such procedure should:

• describe how to upgrade the version of the node
• describe the steps to be taken by the application owner to prepare the application to have its history rewritten
• describe how to check that the application state was kept after the upgrade is done
• identify potential issues and propose solutions
• list the requirements to follow the procedure (e.g.: tools, permissions etc)
• provide examples of step success where applicable.
• test on an environment that replicates "production" (if possible).
• add a warning that "History contract holds claims for several applications. Changing the History affects all applications managed by that History.

Note

New history instances can be created with HistoryFactory.newHistory()

Note

In order to update an application history, is necessary to call Authority.setHistory()

📈 Subtasks

• TBD

✅ Definition of Done

• Migration guide created (MD document under docs folder with a link from the main README)
• Reproduceable steps demonstrating a test application has been successfully upgraded and its state has been kept after the upgrade

[tuler]

Notice that History contract holds claims for several applications.
Changing the History affects all applications managed by that History.

[marcelstanley]

Done at #507