Fix uppercase bug (issue 63)

Quick fix to keep the uppercase letters in the path for the generation of Kotlin classes.
It was only tested on my (linux) computer.

See https://github.com/dukeboard/kevoree-modeling-framework/issues/63 for further details about the bug.
Nop. 
This applies to the Packages defined into you MetaModel (thus does not solve your issue).
And packages have to be in lower case otherwise generate some errors here and then.