Ability to store xbcloud parameters in a cnf file

For security, we may want to add an option for xbcloud to read swift parameters from a .my.cnf section in the users home directory or alternatively in the global /etc/my.cnf or /etc/my.cnf.d/*.cnf similar to the feature in the mysql client.

This way, we would not be passing sensitive data such as --swift-key on the command line.