Update for ZED SDK 2.8 (stereolabs#76)

Stable API (stereolabs#62)

* API break, major changes: removed Py prefix, move to unified sl namespace

Fix stereolabs#60 mem leak PyMat get_value

ZED SDK 2.3 features stereolabs#52

- mem leak fix struct
- add function getDeviceList with associated struct and enum

Update for ZED SDK 2.2