Issue #758 workaround

Common place to store images that are likely to be shared across pages.

• Icons - Generic icons like arrows, calendars, "New" balloons and so on.
• Logos - Logos for specific organizations, events, programs, etc.
• Screenshots - Galaxy screenshots used in this web site.
• ScreencastFrame - Supplemental graphics used for tutorials and quickies.
• NewsGraphics - Graphics used in communications, such as Galaxy Development News Briefs. May have a date stamp.
• Learn - Graphics are generally UI screenshots used in Support and Learn wikis.
• Photos - Photographs.
• NGS101 - Graphics used in NGS 101 tutorial page.