with this patch, navigation with the browsers forward/backward buttons
is supported within topics and subtopics as well as deep linking into
topics using hashed urls like /gui/#Map or /gui/#Environment/Weather
Also, slightly rename map overlay layers
- show at least one stopwatch
- add a refresh button (for web-apps)
- no-cache for index.html
- reorder buttons for Aircraft topic
- add aircraft thumbnail to Aircraft topic
