Consistency Problems for Properties: Service Properties vs. Controller Properties

[jo-bru]

Some properties (let's call them controller properties) such as angles are stored on the controller and therefore are fetched by sending a request to the controller.

Others (let's call them service properties), like last_used_angles are only stored as a property of the XArmAPI* api object (xARM-CPLUS-SDK) and are therefore not fetched from the controller.

Controller Properties are consistent over different sessions (session = initialization =>disconnect), on the other hand, Service Properties are reset every time a new session is started by calling initialize.
This is probably desired but still might create some problems (e.g. see Issue #44 ).

This might also be interesting for multi-user applications.

Needs to be further discussed and investigated..