Move all migrations to separate file

Also fixed some inconsistent uses of snake case.

config.go

@@ -151,53 +151,3 @@ func (app *appContext) loadConfig() error {
 
 	return nil
 }
-
-func (app *appContext) migrateEmailConfig() {
-	tempConfig, _ := ini.Load(app.configPath)
-	fmt.Println(warning("Part of your email configuration will be migrated to the new \"messages\" section.\nA backup will be made."))
-	err := tempConfig.SaveTo(app.configPath + "_" + commit + ".bak")
-	if err != nil {
-		app.err.Fatalf("Failed to backup config: %v", err)
-		return
-	}
-	for _, setting := range []string{"use_24h", "date_format", "message"} {
-		if val := app.config.Section("email").Key(setting).Value(); val != "" {
-			tempConfig.Section("email").Key(setting).SetValue("")
-			tempConfig.Section("messages").Key(setting).SetValue(val)
-		}
-	}
-	if app.config.Section("messages").Key("enabled").MustBool(false) || app.config.Section("telegram").Key("enabled").MustBool(false) {
-		tempConfig.Section("messages").Key("enabled").SetValue("true")
-	}
-	err = tempConfig.SaveTo(app.configPath)
-	if err != nil {
-		app.err.Fatalf("Failed to save config: %v", err)
-		return
-	}
-	app.loadConfig()
-}
-
-func (app *appContext) migrateEmailStorage() error {
-	var emails map[string]interface{}
-	err := loadJSON(app.storage.emails_path, &emails)
-	if err != nil {
-		return err
-	}
-	newEmails := map[string]EmailAddress{}
-	for jfID, addr := range emails {
-		newEmails[jfID] = EmailAddress{
-			Addr:    addr.(string),
-			Contact: true,
-		}
-	}
-	err = storeJSON(app.storage.emails_path+".bak", emails)
-	if err != nil {
-		return err
-	}
-	err = storeJSON(app.storage.emails_path, newEmails)
-	if err != nil {
-		return err
-	}
-	app.info.Println("Migrated to new email format. A backup has also been made.")
-	return nil
-}