Reduce token bucket refill interval

With respect to ticket legacy/trac#2536 (moved) (Disable outgoing token bucket...) and in order to meet Nick's suggestion to split up the original proposal, this new ticket deals with the token bucket refill intervals only.

In particular we propose to reduce the refill intervals (see attached proposal).

To some extent the implementation of an additional parameter that sets the refill intervals has already been reviewed by Karsten and Sebastian. I attached a patch that is based on Tor's git repository (commit e98e1c83) as basis for discussion.

Trac:
Username: Flo