Add automatic tests

[flavio20002]

Add new structure for automatic test and some use cases as well:

• It includes two new workflows.
  • One that is executed automatically on push and pull request called "test"
  • One executed on demand called "update-tests" that can be used to generate the reference pngs and download them on the computer. Useful if the person is not able to launch the script locally.
• The test case support multipage output (for example when testing #only and #uncover ). The test script automatically check all the output pngs versus the reference png committed with the repository.

[flavio20002]

I will adapt to the new structure soon

[flavio20002]

Ok, now i'ts ok!