Use 'ext' for custom properties.
Fix to get 'gradle tasks' working.
Update wrapper to Gradle 1.2.
Add 'plugin best practices' to index page.
Update info on getting approval for publishing.

The HOWTO on migrating to the new plugin repository said that developers had to
submit plugin approval requests via the developer mailing list. This is no
longer the case as they should submit them via the plugin portal.