Case added to prompt user for salt value

Script should now prompt the user to enter a salt value, or to generate
a new one. If the user leaves the field, blank, the script will generate
a new salt value. if the user enters a salt value, then the script will
accept the user provided value.
Added validate_salt function

The validate salt function will either generate a salt for the user or
allow their supplied salt through.
Added prompts for salt value

Prompts should now be displayed to the user for entering their salt
value.