open settings command

1. Adds menu item "Open Preferences File" to Debug menu to open settings file
2. Adds command CMD_OPEN_SETTINGS
The command 
1) Get the location of the user prefs file from PreferencesManager
2) stats the file
3) if it exists it is opened, if not an empty file is created and opened



Old description:

1. Adds menu item "Open settings" to help menus to open settings file
2. Adds command CMD_OPEN_SETTINGS
The command 
a) Get the location of the user prefs file from PreferencesManager
b) stats the file
c) if it exists it is opened, if not an empty file is created and opened