Simplify the application appicon creation

Simplify the application appicon creation

This patch removes all the appicon stuff from the application creation
to the appicon creation. Now, the application only calls one function
(create_appicon_for_application()) and this function do all the work.

The function do the same code than the code before this patch, but the
only change is that the "if" test to check if the appicon was found in
the docks now is negated, removing the return and doing the appicon_save
inside the function.

Finally, the old makeAppIconFor is now create_appicon_for_application().