NamespaceService: mark it as an ImageJService
NamespaceService: mark it as an ImageJService

Without this, it is excluded from the context when using
"new net.imagej.ImageJ()" which causes dependent plugins to fail.

In particular, the NamespacePreprocessor requires this service.

gab1one/imagej-ops,stelfrich/imagej-ops,imagej/imagej-ops