Logging

This release adds logging! Vibe logging for builds that use vibe, and std.experimental.logger otherwise.

Note that if you are using DMD prior to version 2.099.0 (or a compiler based on such a front end), the default log level for std.experimental.logger was to log everything (including trace messages). Therefore, just using the library will spew all trace and debug messages unless you either use version 2.099 or later, or set the default logger level before using the library. If you use vibe with mysql-native, this should not apply to you. For this reason, even though there are no API changes in this revision, it is a minor version bump so as not to surprise those depending on the prior release.

Thanks to @SingingBush for the efforts to add logging!