Camera

* Fixed the invisible `UsingCamera(string)` method on `IAppConfigurator`
* Added the ability to more usefully extend `ICamera` by injecting in instances of `IWebDriver` and `ITakesScreenshot`
* Added proxy interceptor so that logging and screenshot taking automatically happen for all Seleno calls :)
* Added breaking change note about the exceptions thrown from Seleno - note: this warrants bumping Seleno to v0.8 - **change the CI server version before merging**

cc @bendetat @mehdik @mwhelan