Allow Project-Level config of Display Line Annotations

Inline annotations / error markers are useful while developing a project; but they are superfluous while exploring third party code. I don't want to disable the display of line annotations globally, but would like being able to do so in the per-project settings.

Attached is a screenshot of how the editor looks like after importing into Qt Creator the source code of GLib2.0; this should make it evident why disabling inline annotations is desired. The source code was imported with the "Import Project" / "Import Existing Project" template, exclusively for reading and exploration purposes, to leverage the "search project" and "follow symbol" functionalities of the IDE.