Merge pull request #242 from Ansa89/trivial-fix

Usage help: add missing comma
update DHTnodes, small fixes
Add TCP nodes on 443
possibly fix display bug on some platforms
remove duplicate DHT node
add option to unencrypt an encrypted data file
improve behaviour of misused encryption options
add setting to disable welcome message
bump version to 0.5.1
Makefile: use single quotes also for PACKAGE_DATADIR