code-gen schema files for fabric plugin

[gashcrumb]

Currently the schema behind the create container stuff in the fabric plugin is fetched as needed to generate the forms. Might be better though to just codegen these as part of the build instead, as if you run hawtio as a separate process and use the JVM tab to connect to fabric the schema is unavailable unless you install the hawtio-json-schema-mbean module into the JVM you've connected to.