Add executor for multithreaded search

[hextraza]

• Multithreaded search and faster page 1 loading times
• Minor change to modify the message when the client errors
• Changes the table's pagination message in the bottom-right to read "More than x" where x is the current page size, instead of 1000. Lucene doesn't have a good way of returning the number of pages that a query would hit without executing the whole query, which would probably be pretty slow, so removing the # of rows entirely makes the most sense to me. I could return an exact number if we were ok with the query being slower, however.
• Change some client behavior around resetting to page 1 when there's a new query or the pageSize changes.