Merge branch 'fix/putImageData' into develop

putImageData fix done, incorporated in develop
First part of off screen canvas fixed: drawImage recognizes canvas
Fixed first part of the problem: differenciation between image and offscreen canvas.
Fix globalCompositeOperation. Blending functions still need reviewing.
Merge with latest develop.
Added EJCanvasBlendColor functions.
Removed code part specific to Ejecta iOS since blend functions are different.
Merge branch 'develop' of github.com:aogilvie/Ejecta-X into develop
Merge branch 'develop' into fix/globalCompositeOperation
Merge branch 'develop' into fix/globalAlpha
Merge branch 'develop' into fix/offScreenCanvas
Fix crash when using multiple canvas on Android 2.3: buffers are no longer generated manually at onscreen canvas creation.
Merge branch 'develop' into fix/globalAlpha
Merge pull request #3 from jrouault/develop

Fix globalCompositeOperation not properly assigned. Fix globalAlpha and clearRect. Fix offscreen canvas.