Improvements for the updater on the manager

[Senyoret1]

Did you run make format && make check?
Yes

Changes:

• Now, before updating a visor, the manager checks if there is an update available, blocks the operation if there is not and shows info about the versions.
• The update procedure was modified to work with the changes made to the API endpoint.
• The Spanish translation was updated.

NOTE: for this PR to work, the changes made in #217 are needed.

How to test this PR:
Use the update button on the visor details page.

[Senyoret1]

The lastest commit also fixes the reboot functionality of the manager, as #214 changed the API endpoint to work with POST request, instead of GET request.