Move success and failure messages to the server.

[JeroMiya]

Currently angular2's built-in localization library does not support scanning and extracting localization strings from code. Our current success/failure messages come from the code and can't be localized. As a temporary workaround (there is an issue on the angular2 github page to add this) move all success/failure messages from the frontend code to the backend code.

This issue also implies adding string localization to the backend code using standard .net and asp.net core localization functionality.