backend:
* add low priority mode (nice level 10), disabled by default
* enhance 'Force DNS' to redirect ports 53, 853 and 5353
frontend:
* switch to dynamic XHR polling for runtime information and logfile
viewing
* add new 'Refresh' button to reload blocklists
* various cleanups & small fixes
Signed-off-by: Dirk Brenken <dev@brenken.org>