Add `avoidCss3dTransforms` flag

CSS 3D Transforms are used to set DOM entities position, this should
increase performances as these operations are hardware-accelerated but
using them for positioning makes CSS effects unavailable.

By setting this flag to true you can force DOM entities positioning
using left and top CSS properties.
Merge pull request #609 from potomak/feature/optional-css-3d-transform

Add `avoidCss3dTransform` flag