Flash additional partitions

I don't have the time for now, but we have to double-check the behavior of 8c6183e since it seemed to be related to the user error in #516 while tested the config file the first time.

Also, maybe we should add a button saying something like "The developer of this ROM ask to flash another file", and if ticked, show, even if it's not in the config file, the menu to flash all additional partitions (without developer mode or so). Because it seems to depend heavily on the ROM, even for the same device...
What do you think?

[tsterbak]

That sounds like a good idea! I will add it to the next release roadmap! :)