Add packaging and publishing of templates to the core

[pledbrook]

As discussed in issue #78, it might make sense to have at simple mechanism for packaging and publishing templates built into the core library. The Gradle plugin (and potentially a Maven plugin) will then depend on the core library for much of the behaviour, such as zipping and pushing to Bintray.

[kyleboon]

If packaging and publishing are in core, then what's the value of the gradle plugin? Its difficult to use outside of the actual lazybones project anyway.

[pledbrook]

The Gradle plugin allows people to incorporate packaging and publishing of templates into a larger build. It looks like this may happen with Ratpack and its templates. I think the plugin also makes it easier to manage multiple templates. I think any support in core would be fairly limited.