MTR options from .cnf config file and features

1. Config file by default is located in HOME/.mtr-mariadb;
2. Config file format is compatible with server conf file. So server config can contain MTR sections;
3. Default section is [mtr], if section name is absent in the beginning of file it is treated as [mtr];
4. We can set file location and section name from command-line or from envirnment;
5. Command-line options take precedence over configuration file, environment variables take precedence over command-line options.
6. If some code is taken from CPAN its license must comply with our licensing requirements;
7. If there is wrong setting in configuration file MTR fails and displays the error message. It is clear from where it comes: conf file or command-line.