ofxiOSVideoPlayer API updates

- replaced getPixelsRef() with getPixels()
- replaced getTexture() with getTexturePtr()
- introduced ofPixels and removed old `unsigned char` pixel arrays.
- replaced pixel order swizzling functions with vImage methods from
Accelerate framework (same as in the OSX version of AV video player)
- updated ofxiOSVideoPlayer example with the API changes.
- added Accelerate.framework to iOS template project.
Merge pull request #3352 from julapy/ofxiOSVideoPlayer-api-updates

ofxiOSVideoPlayer API updates
ofvbo refactor wip

+ makes all utility methods pass through programmable attribute pipeline
+ makes sure all attributes are cleared when calling ofVBO::clear() - this wasn't the case for custom attributes
+ automatically assigns standard attributes to built-in pipeline when using utility methods or hand-setting attributes
+ unifies execution pathways by following the DRY principle
+ allows for 3d texture coordinates.
Fix for https://github.com/glfw/glfw/issues/222
cleanup
set VertexAttributeLocation (fixes programmable GL Renderer)
make sure to only activate custom attributes in fixed function renderer.
Merge pull request #3354 from procedural/glfw-missing-header-fix

Fix for https://github.com/glfw/glfw/issues/222
minor fixes in ofBufferObject

+ GL methods concentrated in ofBufferObject::Data to follow RAII idiom
fix non c++11 evaluation of shared_ptr
whitespace fixes
Merge pull request #3355 from tgfrerer/refactor-ofVbo

refactor ofVbo - ready to merge
ofxiOSVideoPlayer getPixels() fix.

- fix for recursive getPixels() call.
- added one more deprecation message that was missed previously.
Merge pull request #3361 from julapy/ofxiOSVideoPlayer-getPixels-fix

ofxiOSVideoPlayer getPixels() fix.
ofxiOSVideoPlayer getPixels fix.

correct implementation of `const ofPixels &
ofxiOSVideoPlayer::getPixels() const`
Merge pull request #3364 from julapy/ofxiOSVideoPlayer-getPixels-fix

ofxiOSVideoPlayer getPixels fix.
Merge branch 'master' of https://github.com/openframeworks/openFrameworks.git into rexgo