Add flag to allow Wayland clients external to AppMan

Setting "noSecurity: false" in Qt Application Manager will disallow Wayland clients that weren't started by AppMan to map a surface in the application manager, [1]. However, we rely on being able to do this.

A new property shall be added to AppMan's yaml manifest to allow external Wayland clients to connect while still allowing "noSecurity" to be disabled, similar to how it was done with "allowUnsignedPackages" in [2].

[1] https://code.qt.io/cgit/qt/qtapplicationmanager.git/tree/src/window-lib/windowmanager.cpp#n826
[2] https://code.qt.io/cgit/qt/qtapplicationmanager.git/commit/?h=5.15&id=f3f519ad9fafefebae5dc7099e2f81da109b2c2e