Rearranged camera code:  - moved pvcam-specific code out of generic cameraland  - Camera may no longer access camera drivers directly; all access must pass through the device first.  - changed generic camera API a bit--replaced lastFrame() with newFrames()
Rearranged camera code:
 - moved pvcam-specific code out of generic cameraland
 - Camera may no longer access camera drivers directly; all access must pass through the device first.
 - changed generic camera API a bit--replaced lastFrame() with newFrames()

ibressler/pyqtgraph