Should we use os.UserCacheDir for database?

[larsks]

Currently, nom stores the database adjacent to the configuration file. Would it make sense to move this from os.UserConfigDir() to os.UserCacheDir()? That is, use $XDG_CACHE_HOME instead of $XDG_CONFIG_HOME.

[guyfedwards]

The thinking here is that you may want to version control the DB as well and so having it all in a single location is easier. We could allow the db location to be configurable if users want to have it at XDG_CONFIG_CACHE or elsewhere