implement new primo-style search box

[maxstarkenburg]

See this branch for reference (though it contains really junky code done for quickly mocking up for user testing purposes).

[maxstarkenburg]

Still need to do before sending pull request for review:

• Run some local accessibility testing using something like the SiteImprove browser extension (homepage and internal pages). Possibly need to add attributes like aria-controls to the scope dropdown?
• Test on other browsers and devices besides my Windows Firefox (homepage and internal pages).
• Remove references in code to things like findit/articlesplus/classic-catalog/bento/etc. These should mostly just be in the menus (at least in terms of theme code), I think.

[maxstarkenburg]

@rdelaloy and @qbaron: Seeking your input on the blue navbar menu dropdown under Research. Currently the links (at least for Gelman) in the first section look like:

~~Find Books & Media Journals | Tutorial Subject Databases | Tutorial ArticlesPlus | Tutorial Classic Catalog GW ScholarSpace~~

Classic Catalog is easily enough; we'll just remove that line. Should "Books & Media" be replaced with "Catalog" and point to an empty catalog-scoped Primo search? Should "Journals" point to https://wrlc-gwu.primo.exlibrisgroup.com/discovery/jsearch?vid=01WRLC_GWA:live? Should "ArticlesPlus" be changed to "Articles" and point to an empty articles-scoped Primo search?

See #142 for menu change decisions.

Presumably things like those HowDoI/Tutorials will need to be updated. And we can use the "Search and Replace Scanner" to find some of the other content that needs updating, but I don't think that tool searches blocks or sidebar menus. I noticed, for example, there's a link on a page like https://library.gwu.edu/search/node?keys=blah to "All Search" (Bento) that's in a block.~~

[maxstarkenburg]

Code bug found: To reproduce:

• Type something in the search box.
• Tab so that focus goes into the new dropdown that appears below the search box.
• Keep tabbing past all those options so that focus ends up in the dropdown to the right of the search box.
• While focus is on one of the options that isn't "Library Website", hit Enter.
• Find yourself in the library website search instead of Primo.

Seems to happen on all of FF, Chrome and Safari on Mac. On both homepage and non-homepages.

Note to self: Be careful not to break things for the case where nothing was typed into the search box (where hitting Enter while focused on of the right-hand dropdown options throws your focus back into the empty search box).

[maxstarkenburg]

Except for the aria attributes and perhaps other accessibility-related improvements that we're not so sure about, this is now done.