Configuration for RemoteWebDriver Drone extension

See top-level task for details of reusable session feature.

The support for RemoteWebDriver should be part of Drone, including configuration, but it has been prototyped in Graphene, to allow introduce the feature quickly.

Right now, configuration is hard-coded to Firefox:
https://github.com/arquillian/arquillian-graphene/blob/feature/quick-turnaround/graphene-webdriver-drone/src/main/java/org/jboss/arquillian/graphene/drone/factory/RemoteWebDriverFactory.java#L78

Allow to configure the RemoteWebDriver browser in arquillian.xml.

The RemoteWebDriver configuration differs from other types.

If necessary, RemoteWebDriver can be moved to Drone at this point and whole configuration might be addressed there.