Use KDevelop::htmlToPlainText where applicable

(cherry picked from commit e7142f5bb3fb0e6ddc54a8156b2b7aca05627ee9)
ProblemReporter: Improve appearance of the list

(cherry picked from commit 22dc8ce5fe90c610cb4cfed4bc152ea5abadc3b0)
Detect more common Qt runtime warnings

This time for QObject::connect

(cherry picked from commit ee9eafb1bc7ac64a8726241cd258756fd34ab205)