#86 default layer sorting order

[Pela R. Donable]

The current layer sorting seem random and always has to be changed to be useful.
A better option would be to have the layers sorted per a saved default, according to the Gerber file extension name.

[Joel]

If I can add something, that also is related to feature request #85, it would be great if it could be user configurable. Not all the programs output gebers with the same names, so if we had the option to tailor it with regexp, for example, that would be brilliant!

[Pela R. Donable]

It is now 8 years later, can we fix this simple thing?