Static Builder class generator plugin for MyBatis Generator

Hi!

I have written a new MyBatis plugin to add a static builder class for a domain class. I haven't tested it because I don't know how to access the mybatis-parent POM, but I think it should do the job.

This is my first pull request on Github, so please guide me if I've made any mistakes.

Please review and eventually merge it.

Thank you,
Silviu BURCEA