UI fixes

'light' theme (console & apps):
- Rework to reduce contrast (ticket #1996)
- Add custom radio/checkbox icons for Chrome/Blink

Console:
- Fix reseed failure notice overlap when "check connection" message shown
- Enhance presentation of console "error 500" messages
- Cosmetic tweaks to welcome page presentation, arabic welcome page tidyup
- Migrate .smallhead th class to tr to simplify markup
- Sidebar:
  - Remove "Congestion" from default sidebar (still present in default
    advanced sidebar)
  - Fix label wrapping issue with translations
  - Migrate sidepanel news section to tables to permit better control over
    wrapping and placement (ticket #1996)
  - Move news item dates to tooltips to lessen chance of headlines wrapping
    and cleanup presentation
  - Increase maximum length of local tunnel links in the sidebar (and handle
    overflow with CSS) to minimize chance of default tunnels display
    truncating in translations
  - Add the power off icon to sidebar restart button on hover to clarify
    button function (ticket #1996)
- /configadvanced: Move floodfill status to row above to remove unnecessary
  whitespace and cleanup UI
- /debug: Add debug icon to h2 headers to aid navigation
- /graphs: Improve presentation of graph images by removing rendered border
  and setting background color to better integrate with themes
- /home: Widen div.app to lessen chance of truncation (classic/midnight)
- /jars:
  - Minimize table overflow with conditional scaling of content
  - One-click select for revision, sha256 & unsigned mods
- /logs:
  - Reduce line/entry spacing for router and critical logs (#ticket 1996)
  - Multi-column view for changelog at >=1400px to address horizontal
    whitespace issue
- /netdb:
  - Multi-column display of Leases in LeaseSet tables
  - Better alignment of Lease elements, iconify gateway
  - Placeholder flag for unknown/unresolved peers for [flag+dest] combos to
    improve presentation / fix deadspace issue
- Chinese:
  - Fix alignment of table contents in /tunnels (classic)
  - Fix sidebar content display width (midnight)
  - Cosmetic fixes (all themes)

I2PTunnel:
- Ensure message log font scales proportionately
- Fix overflow issue with dropdowns in Chrome/blink (dark/midnight)

SusiDNS
- Reduce width of filter buttons to lessen chance of wrapping (ticket #1996)
- Add non-selectable items to improve copy/paste of hosts in address books
- Make dest addresses in host list only display scrollbar on focus to reduce
  screen clutter
- Hide broken imagegen images

SusiMail: Enhance presentation of 'postman' links on login panel

router/java/src/net/i2p/router/transport/CommSystemFacadeImpl.java

@@ -523,6 +523,8 @@ public class CommSystemFacadeImpl extends CommSystemFacade {
             buf.append(countryName);
             buf.append("\" src=\"/flags.jsp?c=").append(c).append("\"> ");
         }
+        else
+            buf.append("<img class=\"unknownflag\" height=\"11\" width=\"16\" alt=\"??\" src=\"/flags.jsp?c=a0\" title=\"").append(_t("unknown")).append("\"> ");
         buf.append("<tt>");
         boolean found = _context.netDb().lookupRouterInfoLocally(peer) != null;
         if (found)