UI updates and other improvements

Hello, opening a pull request for changes I've made for the plugin.

Changed the UI to allow for searching of users, while still retaining
old functionality.  Added confirmation table so the user using the
plugin can see the users they are merging, as well as final warning.
Also updated database supported functionality as not all MySQL database
engines support transactions.  Finally added configuration option to
make it optional to suspend the user.

there is still one change I'm working on in terms of quiz attempts clashing upon merging.