This commit modifies the logging to also log all output to a rolling log
file in the btcd home directory under the logs folder. It uses a maximum
size of 10MB per log file and a max rotation size of 3. This means the
log files will not exceed 30 megabytes.
Also, make every subsystem within btcd use its own logger instance so each
subsystem can have its own level specified independent of the others.
This is work towards #48.
This commit is a first pass at improving the logging. It changes a number
of things to improve the readability of the output. The biggest addition
is message summaries for each message type when using the debug logging
level.
There is sitll more to do here such as allowing the level of each
subsystem to be independently specified, syslog support, and allowing the
logging level to be changed run-time.
