Make kdevelop-app and kdev-plugins use Qt5 resources for splash, rc, knsrc
Summary: If resources are not found in filesystem, they will be read from binary via resource path
Test Plan: Compile, remove file from 'regular' system locations, ensure related feature still functions
Reviewers: kfunk, mwolff, KDevelop
Reviewed By: kfunk, mwolff, KDevelop
Subscribers: kdevelop-devel
Projects: KDevelop
Differential Revision: https://phabricator.kde.org/D529