Allow PCSX-Redux users to save state to a named file and load state from a named file

[ghost]

Sometimes named states can help the user to remember when he or she created it, whether this is a good or bad state and etc.

When the state of the game is very valuable for the PCSX-Redux user the user might want to save the state, give it a name and even save it on his cloud!

To the File menu add two commands:

1. Save state to a file...
2. Load state from a file...

When the user chooses "Save state to a file..." a file browser dialog appears where the user can choose where to save the state and how to name it.

When the user chooses "Load state from a file..." a file browser dialog appears where the user can open the state file that he or she wants to load, which was created earlier by "Save state to a file..."