Update version to 0.2.1, lots of bug fixes and cleanup

* Hopefully fixed Oxmin and Flags support. Please test.
* Fixed commands only working on the command user.
* Fixed messages not showing the command user name instead of the target user name.
* Fixed attempt to index global 'oxminPlugin' (a nil value) error when using commands without admin.
* Added invalid command syntax help, and enabled the Oxmin help.
* Added options to enable/disable messages and notices.