More persistent way to distinct non-config and config sites

[molefrog]

In our current implementation we rely on the content of /tmp/cache/<site-name> folder. There is .forge-config meta file for the sites that have .forgerc file: we actually need it for the Nginx to check if the site needs caching. There is as well .forge-meta.json file with some meta information but it can be recreated on-the-file using Forge API.

However, .forge-config is only created after the deploy (deleter process) which means that the site will lose the config file features if the cache was cleared.

Think about more persistent way to store this information. Also check that all the apps handle www. prefix correctly.