added Prmd::Template::load() to load template with fallback
divide schemata templates into several parts; main, helper (logic) and link. The link partial also contains link_curl_example sub-partial which has many logic
changed render to require a path to template directory instead of path to schema.erb; it enables to extend *only* schemata.erb without a copy of the original schema.erb
fix link_schema_properties.erb is always used fallback-version since link.erb looks up wrong path of link_schema_properties.erb
Merge pull request #112 from co3k/enhance-template-customize

Enhance template customize (devide and allow missing some template files)