Allows scenario annotation with key:value syntax

Hi!

I've extended the @browser tag principle to match any @key:value tags. I needed it for a multi-language site (needed to test all the sites but the language did not impact the test logic).
I've let the IoC for the browser tag but any other @key:value tag is stored in the scenario Context as is.

Updated test cases are provided with the update.

We use it since July and everything's fine in our company. If you think that it could be useful to other people, feel free to merge it.

Regards,
Benjamin