Xcode 6 upgrade.
added setter for texture parameters. Fixed creation values.
added "remove all" capability to GLDrawCommand for uniforms/textures/attributes.
added CoreVideo-specific category to GLTexture to derive textures from CVPixelBufferRef using a texture cache, including RGBA/R/RG (RGBA  & 420v/f Lum/Cr/Cb ) formats. Category is in a separate static lib target, to allow using CeedGL without CoreVideo.
updated targets (all libs, iOS/Mac) to use ARC.
added API to discard framebuffer attachments.
workaround to shut up linker warning (no symbol in static lib).
added support for half float textures (CoreVideo pixel buffers).
texture internal format is now determine directly from the pixel buffer type. (enum -> plane index)
added description to GLTexture for easier debugging.
additional consistency checks (no destroy if handle owner is set) + unbinding of textures after drawing.
now storing GL texture type in wrapper (needed when reading back with glReadPixels).