Tech refresh plus MVP

Hello Petter.  I spent some time updating Vaadin Spring Boot to use the latest Spring Boot version (1.1.5.RELEASE) at the time of this writing. As well, I updated all references to `vaadin.version` to be `7.3.0.beta1`.  I also, revved the `SNAPSHOT` version to `0.0.3-SNAPSHOT`.  

Next, I added a couple of projects: `spring-vaadin-mvp` and `samples/mvp-sample`.  The former is just a base class and an annotation, plus a unit test. The latter is a full-blown app that really leverages all the goodies you and Josh have provided trying to demonstrate MVP in action.  I hope you will take this into the master.  I also have some other ideas I'm working. Feel free to reach out.  Thanks, Chris.