ButtonWithProgressVM

ButtonWithProgressVM implementation based on SimpleButtonVM. This entity can be used by different components to represent a simple button with a progressBar associated.
Can you change the new loading state sentence ``` loading = false ``` and ``` loading = true ``` before the ``` notifyShowProgress() ``` and ``` notifyCloseProgress() ``` . If someone check if the progress is enabled as result of the notify call and you don't update the value before the notify call you'll have an bug :)