Tracker improvements
Added support for iterator remove for cachemap -> only key is supported,
value is not
fixed relay issue with signed packets
update to latest mapdb version
proper return value
Merge remote-tracking branch 'tomp2p/master'

Conflicts:
	nat/src/main/java/net/tomp2p/relay/RelayForwarderRPC.java
	nat/src/main/java/net/tomp2p/relay/RelayRPC.java
	nat/src/main/java/net/tomp2p/relay/RelayUtils.java