* installer.LuetRepository is now installer.LuetSystemRepository,
a struct that extend config.LuetRepository
* config: system_repositories option is now "repositories".
This resolve viper issue.
* config: cache_repositories option is now "repetitors"
This resolve viper issue.
* cmd/*: Now use new config.LuetRepository
* cmd/search: now create local luet repository if database_engine
is equal to "boltdb"