Add -P argument to qmlscene to specify plugins search path

Allow users to specify locations of compiled QML plugins.

Change-Id: I0ad764282a7891013ce0cfa008a1cf8164cb083b
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Add -plugins argument to qmltestrunner to specify plugins search path

Allow users to specify locations of compiled QML plugins.

Change-Id: I66059dc7b1314ca6fbef87032b16ccf3caf8bd30
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>