Implement SecureStrng into LoginDialogData and ShowLoginDialog

[manbeardgames]

This is a feature request, if already implemented I'm unable to find it.
The ShowLoginDialog and ShowModalLoginExternalboth return a LoginDialogDataobject. The implementation of these two dialogs use a normal Textboxfor the password input and place a plain string in memory when put within the LoginDialogData. If possible, please give an option to use a PasswordBoxinstead of the TextBoxand return the SecureString object from the password box.

It's a counterproductive to have he password as a plain string in memory and then having to convert it to a SecureStringafter the fact.

[punker76]

@dartvalince The usage of the SecureString will be available in 1.4.0