BItem.setProp is incremental and not atomic. Replace with BItem.setProps and a complete action

[Misterblue]

There will be setting of several Ability properties that need to happen together (atomically). For instance, setting AssetURL and AssetLoader must be done in URL/Loader order rather than the reverse if setting AssetURL causes the load action to start.
Probably need a setProps that goes through the BItem and to the Ability that can control when actions are fired off because of the setting.