Constants fixes

`Director::PROJECTION_XXX` -> `Director::Projection::XXX`
`Label::TEXT_ALIGNMENT_XXX` -> `Label::HAlignment::XXX`
`Label::TEXT_VERTICAL_ALIGNMENT_XXX` -> `Label::VAlignment::XXX`
`Texture2D::PIXEL_FORMAT_XXX` -> `Texture2D::PixelFormat::XXX`
`BlendFunc::BLEND_FUNC_DISABLE` -> `BlendFunc::DISABLE`
`Transition::ORIENTATION_XXX` -> `Transition::Orientation::XXX`
`Image::FORMAT_XXX` -> `Image::Format::XXX`
`Image::_function()` -> `Image::function()` // private methods should not start with '_'
`DrawPrimitives::drawColor()` -> `DrawPrimitives::setDrawColor()`

Also adds more constant for BlendFunc
And fixes Premultiplied Alpha in PVR v3 images
And tests are updated with the new functions

**IMPORTANT**
JS bindings doesn't compile because the `enum class`, although they are using `int`, they don't have implicit conversions.
So, the JS bindings config file, we need to add a rule that says: `Image::Format` is an `int`, etc...