Support all mysql flags while importing database - #123

Thanks for this first iteration, @abhijitrakas !

First of all, we should add at least 1 test in the Behat suite to test and assert that the arguments are actually passed onto mysql.

Then I have a few thoughts regarding the implementation. You have directly implemented this as part of the db import command now, but I think that every command that works by providing arguments to run the mysql binary would be abel to benefit from this improvement. So I think it would be preferable to implement this in a separate method called get_mysql_args( $assoc_args ) (similar to get_dbuser_dbpass_args( $assoc_args )), and then feed the resulting array of arguments into the run() or run_query() method.