switch to Dancer2 namespace

http://www.sukria.net/fr/archives/2013/02/18/dancer-1-and-dancer-2-what-were-going-to-do/
add the missing test plugin
Dancer2 documentation and packaging, ready for CPAN upload.
versioning format : Dancer2.x.y
remove api_version
no more TODO in ABSTRACT tokens, some documentation cleanup
bump Version
reflect Changes
fix broken t/factory.t test
Propagate context to engines

When the app context is set, use the trigger to propogate the context
or clear the context in all defined engines.