path to .melange in plugin.xml changes overtime and is wrong if the project is deployed

[dvojtise]

from https://gforge.inria.fr/tracker/index.php?func=detail&aid=20139&group_id=4645&atid=13885

the .melange file is referenced in the plugin.xml in order to be able to retreive it from the modeling workbench.

Strangely, the path used may change overtime, sometime this is /src sometime this is /bin that is indicated in the plugin.xml

this is annoying when using git, because the file changes for nothing

more important, neither src nor bin are correct
if these files exists when running in development mode (ie. 2 eclipses) if the language is deployed in an eclipse (in order to be used by a Model Designer) neither src nor bin exists in the final jar.
adding src in the build would be a workaround but this is usually not a good idea to add this folder in the jar (because in general, it would also include all other java and xtend source), a copy in dedicated folder would be much better.