Add UI preferences and simplify config save/load (ref #43)

interface/matrix.go

@@ -32,6 +32,7 @@ type MatrixContainer interface {
 	Login(user, password string) error
 	Logout()
 
+	SendPreferencesToMatrix()
 	SendMessage(roomID, msgtype, message string) (string, error)
 	SendMarkdownMessage(roomID, msgtype, message string) (string, error)
 	SendTyping(roomID string, typing bool)

interface/ui.go

@@ -29,6 +29,7 @@ type UIProvider func(gmx Gomuks) GomuksUI
 
 type GomuksUI interface {
 	Render()
+	HandleNewPreferences()
 	OnLogin()
 	OnLogout()
 	MainView() MainView