Add index searching. Close #1318
Searches should match all keywords.
Fix position of navlinks on Firefox.
Indicate the elapsed time since the last index refresh at the top of the index.
Move the last refresh timer, give the "field" class to the search input.
Smaller search input by default. Hidamarize on hover/focus.
Fix spacing issue for the top right link of the settings.
Add search-clearing button.
Focus the index search input after clearing it.
Prevent content inside of .board from being downloaded on intial page load.

See comments in the code.
Fix the index search clear button appearance on Firefox.
Jump to page zero when starting to search.
Jump back to the previous page when clearing the search.
Rebuild the pagelist when searching.
Add the `Show replies` index setting.
Add a page indicator on OPs in the index.
Replace the times symbol with fa-times. #1338
Use fa-plus for the #add-post in the QR. #1338
Hidamarize the index search input on focus.
Fix font-family of the page num indicators.
Fix relative index refresh date on Firefox.