Adding designersupported to plugins

This patch adds designersupported to the plugins
supported by QtQuick Designer.
Change-Id: I022bdeab6ef1e22dfffd7e1e95b292212aaf10eb
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
Document DropShadow and Glow's transparentBorder properties.

Change-Id: I1f4be68c5b364e5d2151ed26b079a0f00ac31f0c
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
Merge remote-tracking branch 'origin/5.4' into dev

Change-Id: I259099e0d550e5a1f0d6846d6024876d06fa1b4c