Merge pull request #15 from jvelilla/roc_template

Roc template
Removed default_theme.
Update theme and smarty theme description
Fixed non void-safe compilations, and cleaned .ecf files.
+Cosmetic
Update concepts.md

Added references to the important classes.
Removed shared_error from CMS_API
Added Missing theme and Missing tempalte classes.
Updated CMS_RESPONSE to handle missing template and send a 503 status code
with a raw response.