Custom layout, image button and whole toast clickable

Made the code more flexible by adding the support for custom layout,
handling also image button (like the normal button), and adding an option
for making the whole toast clickable (instead of just the button).

Still in principle the desing of the code is constraining flexibility. It
really should allow for Android styling (by default using the app styles).
This change was a minimal change to allow the above with minimal changes to the
interface and following the existing design.