generic AssetData in manifest file

This makes it so that the manifest asset file can be unserialized by
any library by simply defining the basic AssetData and AssetType
classes/enums, or like in OpenFL case - mapping it using a TypeResolver
to a package specific class>

Also adds more info if manifest parsing fails and why.
Asset flat names on iOS removed

in favour of default names, this and the previous commit had the
flatName -> resourceName if this needs to be considered
Minor fix
generic AssetData in manifest file

Making asset manifest completely untyped, resolves issues with Types in
the asset manifest entirely
Adding generic config opaque data for project

Preliminary work, still requires wiring into the templates
Removing erroneous implements Dynamic
fixing null config copy test failures and minor bugs

 (thanks @andyli)