bubbleSort & validated input

bubbleSort code was previously based on example from Exercise 0 document
that only did one pass over the list (in the worst case, a bubble sort
needs to run "n" times for a list of length "n" to move an element from
the bottom of the list to the top).

fixed bubbleSort method so it will only run as many times as it needs to
+ once more to confirm that no swaps occurred.

fixed txtArraySize field to not only display the initial arraySize but
also take validated input. If invalid input is provided, and
btnFillArrayAndDisplay is pressed, the fillArrayRandom() method is given
the previous valid arraySize used, and the text field txtArraySize is
reset to the previous valid arraySize.

invalid values: anything that int.TryParse() can't parse into a 32-bit
integer, and any integers <= 0;