Players should be able to create new users when the game is run from the released JAR

[ashivasubramanian]

1. Do not package Users.xml along with the JAR
2. Check if the Users.xml exists in a known folder on the user's machine.
3. If it exists, read the usernames from that file & show them on the UI
4. If not, show empty users list
5. On creating new users, they must be captured in the Users.xml.
6. On loading the game next time, the list of users should be read from the Users.xml in the standard folder.