Added Preferences table to store user preferences

store/store.go

@@ -37,6 +37,7 @@ type Store interface {
 	OAuth() OAuthStore
 	System() SystemStore
 	Webhook() WebhookStore
+	Preference() PreferenceStore
 	Close()
 }
 
@@ -149,3 +150,9 @@ type WebhookStore interface {
 	GetIncomingByUser(userId string) StoreChannel
 	DeleteIncoming(webhookId string, time int64) StoreChannel
 }
+
+type PreferenceStore interface {
+	Save(preference *model.Preference) StoreChannel
+	Update(preference *model.Preference) StoreChannel
+	GetByName(userId string, category string, name string) StoreChannel
+}