Add namespaces to ZED code

[DanielPD]

Currently the ZED codebase doesn't seem to use namespaces everywhere. Some parts do (e.g. the SDK/NativeInterface classes use namespace "s1"), while the majority of classes don't (e.g. SDK/Helpers/Scripts). This may cause conflicts with other plugins and assets when imported in Unity.

Specifically, I recently ran into a problem using ZED and UMA. UMA defines its own helper classes under its own namespace, which includes a class ReadOnlyAttribute to manage read-only attributes. Similarly, ZED defines a ReadOnlyAttribute class, without namespace, causing a conflict.

[RomanCalderon]

Having a similar issue here. Namespacing all ZED scripts would be very helpful!

[prof-thies-pfeiffer]

In particular the ReadOnly attribute (Util.cs) is used in many assets, e.g. Convai, and each time we encounter conflicts with ZED.