Mobile and accessibility fixes

Related to #96 (closed), #84 (closed)

Accessibility:

• Fix color contrast warnings about white text on blue background
• Add underline on link in footer (not distinguished enough from regular text otherwise)
• Not enough spacing between links in table of contents on about/help pages

Map:

• Move map overlay (with county name, # of issues, etc) above the map. Center it
• Maybe prevent text selection on map
• Fix how GALILEO logo is vertically centered when "Digital Library of Georgia" wraps to more than three lines
• Search box is not quite centered
• Fix warning about unused preload in Safari

Title metadata:

• "About the " button can disappear off screen
• Center blurb under thumbnail (not nesc. a mobile fix)

Page Viewer:

• Add some vertical spacing between buttons at bottom

Advanced Search:

• Margin on city/county multiselects is different than on other inputs
• Clicking on fancy selects/multiselects zooms in a bit which is mildly annoying
• Not a mobile fix, but: "Distance" selector does not need to be a fancy select

Search results

• Depending on the number of results, the pagination might be so close to fitting on one line, but instead the last button wraps