This commit adds environment variable expansion and path cleaning to the
data directory. This allows the user to specify data paths in the config
file such as datadir=~/.btcd/data and datadir=$SOMEVAR/btcd. It also
adds usage instructions and an example to the sample btcd.conf file.
Although not required if the proxy set is indeed Tor, setting this option
does the following:
- Sends DNS queries over the Tor network (during dns seed lookup). This
stops your IP from being leaked via DNS.
- Does not disable the listening port. This allows the hidden services
feature of Tor to be used.