Spring boot project,to enable hawtio to be embedded in Spring boot application

Not sure if this is a direction you want to take or not, but this represents how we are using hawtio with Spring Boot. We wanted to be able to package hawtio inside the application, rather than using the javaagent or the executable war options. This makes packaging and creation of plugins easier (for us).

This change creates a new jar, which is just a repackaging of the web war, moving all the static content to a /static/hawtio directory, which is a directory that will automatically be served by a Spring boot application when this jar is on the classpath of a Spring Boot application (anything under /static/* is served by default). The jar also brings in as a dependency any necessary jars to make this work.

The other changes are:
1) Create a simple mechanism for registering custom plugins
2) Creating a plugin rest endpoint, so that custom plugins can be found by hawt
3) Disable the html5mode so that server rewrites don't need to be configured
4) Modified the existing Spring boot sample to demonstrate usage

When running the Spring boot sample application, hawt will be accessible at http://localhost:10000/hawtio/index.html