add explicit no-cache directive for bootstrap updates

This fixes problems with some buggy servers which are returning HTTP 304 response instead of HTTP 200 response even when no cached copy is available with client or when client makes the initial bootstrap request.
remove some duplicated code
update for weeb.tv changes
fixed invalid frag count detection
fixed wrong timestamps in case of timestamp gap

This fixes issues with http://www.ontvtime.ru/general/tvc.html and probably other streams where only first timestamp is wrong.
added new option maxspeed for control of maximum bandwidth consumption

Fixes #26
quick fix for handling of HTTP status code 503

Fixes #25