Change fgcommand to take an optional property tree root element.
This fixes the animation bindings to use the defined property tree root - to support multiplayer (or other) model that can bind to the correct part of the property tree.
Requires a corresponding fix in sg to allow the command methods to take an optional root parameter.
What this means is that when inside someone else's multiplayer model (e.g. backseat, or co-pilot), the multipalyer (AI) model will correctly modify properties inside the correct part of the property tree inside (/ai), rather than modifying the properties inside the same part of the tree as the non-ai model.
This means that a properly setup model will operate within it's own space in the property tree; and permit more generic multiplayer code to be written.
This is probably responsible for some of the pollution of the root property tree with MP aircraft properties.
Add an additional visibility flag to the menubar implementations,
conditional on whether or not the menubar overlaps the window content.
(I.e for PUI but not Cocoa). This flag is linked to a new property
/sim/menubar/overlap-hide, which the renderer drives off the splash-
screen visibility.
Was only cleaning up the PUI menubar, not old bindings / names. This led to duplicate bindings, each time the GUI was reset, which can happen for various reasons.
Adapt FGPUIMenuBar to use new Locale module.
Adds support for separate "key" property for menu items, so keyboard hints
are no longer part of the item's label (and do not need to be part of the
translated text resources).
