Let's use the java type system
Tries to improve the progress monitor.
Addresses #324. I try to manage my two sub-process as good as I can. The
progress bar will go twice from 0 to 100 while the number on the right
of the window will jump from 0 to 50 (end of the first task) to 100 (end
of the second task).
Merge pull request #382 from agueganno/improvement/progress-bar-legend

Improvement : progress bar in the simple legend editor