Doc: Updated the \brief statements

Most of them were unnecessarily long.

Change-Id: I8942254c2211adb268e399056435e6acc940616f
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Merge remote-tracking branch 'origin/5.4' into dev

Change-Id: I82a85963aa1cc6e0a2cf7a49c039c117948cbeab