KF5: Port KFileDialog -> QFileDialog
Make compile wrt recent changes in kdevplatform
KF5: Port KStandardDirs -> QStandardPaths
KF5: Port KTempDir -> QTemporaryDir
KF5: Remove more references of KDE4 stuff

Changes
- Remove references of KTabWidget/KListWidget
- Remove references of qtest_kde.h
- Remove references of qsplashscreen.h
- Don't use K_EXPORT_PLUGIN
Run test_qtthelpplugin in Ui mode

The documentation controller is required, test is still flaky, though
Get rid off more kdelibs4support usage
file_templates: Add newlines at EOF
KF5: Port to QCommandLineParser and friends
More manual porting from KDE4 headers