Model_Template writes and deletes htm*, txt* files

For the html and txt attributes a file is written to app/tpl/cache when
they are not empty
getContent() returns template bean instead of just the name
region-name is no longer req, added html and txt/text fields
iframe add preview flag
Respects preview flag and uses dynamic tpls if no static one is found
notFound will use only path of the url for domain lookup
Added translations for feature-dynamic-template