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
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.