iOS Examples: add sample code demonstrating multi-threaded OpenGL rendering based on Apple Sample Code

(cherry picked from commit da26a95e)

0-copy is still forthcoming

This removes the aggregation target from the xcodeproj, always compiles both for simulator and device and will solve linking issues in client apps

further, this prepares compiling MVK as a dynamic library

add the podspec file that is adjusted and sent to cocoapods for redistribution of VLCKit via cocoapods