Some fixes for spider, add timeout option

Add timeout option (overall timeout for whole spider operation for one
IP address).
Set default encoding to utf-8, doesn't seem to be auto-detected in all
cases.
German version of Backfire Interface list is now recognized.
Recognize Interfaces in "DOWN" state and ignore those.
Recognize Retries_Exceeded errors from rsclib.HTML_Parse.
Mark unknown exceptions in generated results datastructure.
Add debug option, no debug logging by default, instead log IP address of
current spidered node in tracebacks.
Fix unused interface names in Freifunk interface lists, e.g.
'wan_ifname=vlan1' and vlan1 is not in interface list.
Merge branch 'master' of github.com:FFM/FFM
Fix rounding error in test with python2.6