Modern theme: didnt include this file in last commit.#1737
Set default layout to 3_1_overlay
#1557 Update how slideshow decides what region a block is in and how many blocks are in the regions next door
Fix legacy slideshow #1557

Old slideshow was trying to use image styles from the new slideshow.  I restricted it to use styles starting with slideshow_ instead of merely includgin slideshow_.
Merge in all 3.2 bugfixes from last week