Implement hook_field_prepare_view()

Currently Tablefield data is only prepared during hook_field_presave(), which means that prior to this hook (which is fired on save) the data can not be rendered. Having it renderable means that it could potentially be used in a Node preview, or usable as a Wysiwyg Fields field.

Super simple hook invocation, just needs to iterate over the provided entities and items and pass them through to the existing hook_field_presave() function.

Patch incoming.