feat: add cli parameters for db path and metrics port (#4)

Add support for configuring CLI parameters in the application using a new
`cfg` package. The `cfg` package exports an `AppSettings` struct that
contains the settings the application was run with.
Update the application to use the new CLI parameters to set the db to open
and the port to use for the metrics server.
Add support for setting the app version during build. The app includes a
`-version` flag to print the stored version data.

db/db.go

@@ -10,7 +10,7 @@ const queryBannedIpsPerJail = "SELECT j.name, (SELECT COUNT(1) FROM bans b WHERE
 
 type Fail2BanDB struct {
 	DatabasePath string
-	sqliteDB *sql.DB
+	sqliteDB     *sql.DB
 }
 
 func MustConnectToDb(databasePath string) *Fail2BanDB {