os_slideshow width goes up to 980 for HC.  #1331

Added a new image style for os_slideshow.  Expanded the width's range.

Moved min/max width into options_defaults.  They're not being set by the form, but they should be defined once instead of repeated 3 times over (form def, validate, & error message)
Merge branch 'SCHOLAR-3.x' of github.com:openscholar/openscholar into SCHOLAR-3.x