Mix autoResize + autoFit options, add onOpen and customDialogOptions, and add doxygen comments to Drupal.modalFrame.open()

This is an issue to account for the following changes that I'm about to commit:

a) Mix autoResize + autoFit options.

These options are practically the same thing. They have been mixed into one in Overlay module for D7, and it seems a good idea to do the same here.

b) Add onOpen and customDialogOptions.

These options were also included to Overlay module for D7, and again, it might be a good idea to have them here as well.

c) Add doxygen comments to Drupal.modalFrame.open().