updates related to engine generator

- added --sortable option
- require title attribute or method defined on model
- use namespace as extension name if is present with this logic:
    refinerycms-something -> gem
    refinery_something -> rails engine
    something -> refinery plugin
    Refinery::Something::Post -> namespaced model
updated js with csrf token included to form
update - fix pages title and in generated engines
removed config main_part and rather document that :body part is necessary