Added --plugin option and misc other changes:

* Richer plugin API
* Removed support for `--dotcucumber` and `stepdefs.json`
* The `--format` option is deprecated in favour of `--plugin`
* `@cucumber.junit.api.Cucumber.Options` that was deprecated in 1.1.5 has been removed. Use `@cucumber.api.CucumberOptions`
* Fix android build problems