Reinsert/remove "gt2-" prefix in all module name

We tried to remove the "gt2-" prefix in module names, in order to have <artifactID> matching exactly the directory name. Such match allowed us to remove the <scm> section in all pom.xml files. We also though that a "gt-" prefix was redundant with the <groupId>org.geotools</groupId> declaration. However experience show that it leads to two problems:

• The "gt-" prefix do not appears in the manifest classpath when building a single module (MJAR-61).
• Name clash in eclipse projects when two projects are mounted using maven-eclipse-plugin (MECLIPSE-119)

The path of less resistance seems to reinsert the "gt2-" prefix back in all module names. We would have to reinsert the <scm> section in all modules too, which is error prone. However we would revisit this issue if the above-cited Maven issue are fixed.