Improve use of "#include <QtCore/QSharedPointer>" in codebase.

[odysseus654]

This code review removes #includes for files that don't actually make use of QSharedPointer and adds them where they do.

This strengthens the codebase by:

• removing references to unused libraries
• removing indirect references to QSharedPointer that may be broken on removal of an "unrelated" .h file (or removal of QSharedPointer from that .h file)

(This code review sprouted out of one of the last review checks done before flagging PR 1200 as ready-to-review, the results were unrelated enough to the script engine that I figured it might be worth its own PR)

Testing focus:

• NONE - I don't see any possible effects on the code from this change, this is strictly a compile-time and code-review/coding-style adjustment.