[FEATURE] Represent Selector as Component objects

[JakeQZ]

Part of #1325.

[coveralls]

coverage: 72.749% (+0.1%) from 72.601%
when pulling 9927247 on feature/selector-representation
into 600d163 on main.

[JakeQZ]

Would like initial feedback on this...

There's a bit more to do:

• A few more tests;
• Changelog entries.

It might be possible to break this down into seperate PR, but I can't think how - everything is interdependent.

[JakeQZ]

It might be possible to break this down into seperate PR, but I can't think how - everything is interdependent.

Perhaps an initial change would be to have setSelector() (and the constructor) throw an exception if the selector is invalid, using the existing isValid() method. I wouldn't consider this to be a breaking change, more of a fix, though something that would probably go in the 'Changed' section of the changelog.

[JakeQZ]

Perhaps an initial change would be to have setSelector() (and the constructor) throw an exception if the selector is invalid, using the existing isValid() method. I wouldn't consider this to be a breaking change, more of a fix, though something that would probably go in the 'Changed' section of the changelog.

#1498 covers exceptions possibly being thrown by setSelector() and the constructor.