GWT/GXT Packaging: 215Mb on disk! + Evertyhing is at twice (config + Jahia)

1) On a fresh build install the GWT directories are "eating" 215Mb on disk!!! Unzziping everything is taking about 10 minutes on disk. The Jahia fresh build install is too long on windows now.

2) Moreover they are all replicated twice: one for the config webapp and another one for Jahia webapps.

3) Finally the opening of the tar.gz under windows is firing 80+ errors as name of GWT are too long for windows tmp directories. This is not creating any real issues but this does not give a right feeling for the end-user which is installing Jahia for the first time.