Move index template to its new home.
WIP
Introduce Web::Machine for handling the content negotiation stuff,
more commonly as the REST part.

Engines are now descendants of Web::Machine::Resource (through
Jet::Engine) and can use all the methods there to control the way
through the state machine.

I grab the opportunity to clean up the data structure. Now there are two
main objects; schema holds the persistent data; the DBIC schema, config,
basetypes, renderers and the logger.

body holds the volatile data; the request, stash, basenode and
datanodes.

Jet::Response is out, but may be replaced by something more suitable
later. Renderers are called directly from the engines (with help from
roles, if desired).