Minor code cleanup
Cleanup: length() == 0 → isEmpty()
Cleanup "switch"
* Cleanup the Internet Search context menu (frequenty used items are on top as before)
Use separated "build-kf5.tmp" and "build-kf6.tmp" directories instead of single "build.tmp"
Use Instant::until method
Use "SPDX-License-Identifier" and "SPDX-FileCopyrightText" info in file headers
Use "SPDX-License-Identifier" and "SPDX-FileCopyrightText" info in file headers