send single space to socket if not streaming
and search results still not ready after 10 seconds.
send it every 10 seconds to prevent client from closing socket.
sped up all downloads, json and csv, but not doing "fuzzy"
deduping of search results, but just deduping on page
content hash. added TcpSocket::m_numDestroys to ensure we
do not send heartbeat on a socket that was closed and
re-opened for another client.