Delegate addition in DialogManager and LaunchGate + StringHandler for Localization

[charvoa]

• We added a Delegate in DialogManager in order to know when the "dismiss" button is called.
• We added a Delegate in LaunchGate in order to know if the app needs update or no.
• We added a StringHandler, which is a struct that contains the strings displayed in the popup. Why ? Because, at the moment, we are handling Localization on the client side, and not on the back-end side. So we need to be able to provide strings to display in order to display them instead of the text that's in the JSON.