Update concepts.md

Updated concepts with Modules and Hooks
Update concepts.md

Updated Concepts table of contents
Merge branch 'roc_template' of https://github.com/jvelilla/ROC into roc_template
Added {CMS_SETUP}.modules_enabled: CMS_MODULE_COLLECTION
Updated {CMS_SERVIDE}.intialize_modules to use the new feature {CMS_SETUP}.modules_enabled
Updated cms_hook_block description
Refactor raname {CMS_SETUP}.modules as {CMS_SETUP}.available_modules
Refactor raname {CMS_SETUP}.modules_enabled as {CMS_SETUP}.enabled_modules
Updated code to use the new features names.
Update concepts.md

Updated concepts