Implemented a more flexible blending system (fixes #298)
Created branch for experimental blending mode API

See issue #298.
Based on branch 'new_blending_api' of github.com:tomgalvin594/SFML.
Adjust CMake module to provide correct deps on OSX

Module will now give the OpenGL framework as a dependency instead of the
nonexistent libGL.
Fixed compile error (trailing enum comma) and other minor things
Omitted "Blend" prefix for nested BlendMode enums

BlendMode::Factor instead of BlendMode::BlendFactor
BlendMode::Equation instead of BlendMode::BlendEquation
Improved formatting
Improved documentation
Passed BlendMode objects by const-reference
Improved documentation for sf::Shape and derived classes
Fixed compile warnings
Added the iOS port
Fixed render buffers not correctly resized on orientation changes
[iOS] Adjusted the code and build files to use Automatic Reference Counting
[iOS] Various adjustements to implementation
Added the Android port
Improved OpenGL error macro

It now supports functions that return values.
Improved OpenAL error macro

It now supports functions that return values.
Adapted the examples for iOS (WIP)
[iOS] Improved support for examples, removed the need for a toolchain file
[iOS] Removed the install rule of the deleted ios.cmake toolchain file