refactored: percona module restructure

* adding rodjeks excellent logrotate module
* code style tidyup
* ensure logrotate file dropped in by the percona deb is absent in favour of our own
* temp disable dropping in a my.cnf until it can be tuned
* break out install perconas apt repo into separate sub class
* logrotate is now managed by logrotate::rules
* remove ugly run stages and set some ordering