Enable HiDPI on OSX for KDevelop

Summary: Enable HiDPI on OSX by adding the necessary key/values to Info.plist

Test Plan: Run and verify on OSX

Reviewers: kfunk, mwolff

Reviewed By: kfunk, mwolff

Subscribers: kdevelop-devel

Projects: KDevelop

Differential Revision: https://phabricator.kde.org/D449