Refactor, cleanup and improvement linked to the pinning feature about chemiscope

[ceriottm]

Re (3) I think that some of that could be done as part of the settings PR. All of those settings-related code could go in a separate file, would be tidier and easier to navigate.

[Luthaf]

• Use a addPinned() function instead of using setter. As far as I understand, a new pinned is currently automagically created when doing map.active = guid with a new guid.

[ceriottm]

Isn't this to be closed? Would be good to clean up a bit the open issues, many seem obsolete

[Luthaf]

There is still a remaining point from the initial comment.