T161 delete news & events menu item

[maxstarkenburg]

Remove News & Events menus:

• putting link to "Events" under "About" now (except there's still a dedicated "Events" button on mobile/narrow screens)
• removing menu links to AT Press Room and Blogs and Social Media entirely
• moving "Vision Magazine" to "About" and replacing "Vision" there with "About GWLAI"
• moving "Digital Showcases" under "Collections"
• scope creep?: also removing "News & Events" from Virginia pages, and removing the "Positions Available" item that apparently wasn't supposed to be there (some discussion of that in #171 instead of #161.
• scope creep: replacing 404 "Grants" link under "Research" (in Gelman, Eckles, and Virginia menus) with "Data Management" libguide.

Fixes #161.

[ok-steve]

Fixed: gwu-libraries/library.gwu.edu#5