refs https://github.com/TryGhost/Team/issues/1070
- added `bread` util that acts as a wrapper for the provided model, if we have any business functionality needed when settings are added/removed then it will go here
- added primary "server" service that handles syncing of custom theme data extracted from a theme with the settings that are in the database and exported as "Service". Syncing rules on theme activation:
- if a new setting is seen, create it with the default value
- if a setting has it's type changed, remove it and create a new setting with the default value
- if a select setting's value is not a valid option, reset it to the default value
- added shared "frontend/server" service that exposes an in-memory cache of key/value pairs for the currently active theme
