Feature - Add mrf variables to template.json

[ajukes]

-Added .gitignore refs for intellij -Converted global_codec_prefs & user_agent_string to user defined template variables.

[davehorton]

looks good, minor requests:

• could we change 'cluster_alias' to 'mediaserver_name'
• could change 'codec_list' to 'preferred_codec_list'?