* Replace logging backend to flexi-logger and add log rotation
* Changed flexi_logger to log4rs
* Disable logging level filtering in Root logger
* Support different logging levels for file and stdout
* Don't log messages from modules other than Grin-related
* Fix formatting
* Place backed up compressed log copies into log file directory
* Increase default log file size to 16 MiB
* Add comment to config file on log_max_size option
* Make grin.toml config optional. Mirror exisiting config parameters in grin.toml to source code, so binary can run without a config file. Add test for it.
* fixup! Make grin.toml config optional
* added mining subview, changed main menu selection
* collecting difficulty stats from miner
* add diff calc view, separate server stats
* rustfmt
* block difficulty data output
* rustfmt
* ensure diff data is always shown
* don't write to stderr when tui running
* added global slog instance, changed all logging macro formats to include logger instance
* adding configuration to logging, allowing for multiple log outputs
* updates to test, changes to build docs
* rustfmt
* moving logging functions into util crate
Gary Yu