Enable more Aqua tests by solving piracy and ambiguities issues

[Tortar]

Fixes #135

This PR is the main contribution to solve #135. But there are some others I will open in other packages, they are required to make everything work.

It removes all avoidable piracies and all direct ambiguities within the package. As a part of it I also addressed a TODO because otherwise some ambiguities were much difficult to solve: I changed all methods such as observable(refs::Tuple{Vararg{RegRef, N}}, obs, something=nothing; time) to observable(refs::Tuple{Vararg{RegRef, N}}, obs; something=nothing, time=nothing), which means that something is now a keyword argument of those functions. This is a minor breaking change so maybe it will require a new major version if we want to be strict about it.

[Krastanov]

Thank you, this is very much appreciated! A new breaking release is reasonable for the change you suggested.

[Krastanov]

The SProjector warning in the doc builder is fixed in a separate PR.

Thanks for coordinating all these fixes! I have noted down this bounty and I will be sending you more details on how it will be processed at the end of the month (it will probably be a slow process, as it is managed through a non-profit -- on your end, you will be asked to fill out a form with payment details, but that is all the boilerplate you need to worry about).

[Tortar]

Thanks @Krastanov for the help in passing CI tests.

Do I need to write an email to you at some address to help processing the request?

[Krastanov]

Yes, please just send along an email with your name and a link to the bounty. NumFocus will contact you directly to get the transfer information.