manifest property usage is only for ogsi maifests

the manifest property of the eclipse plugin is only for the osgi writer and not for the wtp manifest, because the wtp manifest is a special case that will not be included in the maven build just in the eclipse classpath. The problem is that the property has a default value and by that deacivates the WTP classpath!

included a patch for the 2.5 release, including some renaming so it won't happen again.

please release a 2.5.1 version with this patch!