Add a 'CornerstonePreRender' event that is fire before the image is rendered.
Add a 'CornerstonePreRender' event that is fire before the image is rendered.

This allows, for instance, the CINE tools the change the image just
as it is about to be rendered.

adreyfus/cornerstone,cornerstonejs/cornerstone,google/cornerstone,google/cornerstone,adreyfus/cornerstone,cornerstonejs/cornerstone,chafey/cornerstone,cornerstonejs/cornerstone,adreyfus/cornerstone,cornerstonejs/cornerstone,chafey/cornerstone