1. Fixed up Stock screen and buttons en/dis-abling at appropriate times eg. open/save/pick stock or type in
2. Fixed StockCombo on Stock screen so that it shows first item in list
3. Improved the layout in StockController to reflect that when a tab opens is *actually when* the contents are displayed after reading in the model data
4. Added an exception to Crud.java "Is the application / database already open?  "
5. Changed the stock.fxml to what I thought would be a better layout.  But still not there and I have a TODO to use Grid Layout.

TODO -
1. If the application is already open handle that more gracefully than bomb out.  This would require hooks into the OS this is running under so may be beyond the scope of what can be achieved. See Issue #9.
2. Use Grid Layout for stocks.fxml. See Issue #7.
3. Start working to issues and commit to one issue at a time! All issues.