Move the CEV plugin to the common sandbox location

The CEV plugin (uimaj-ep-cev) is a plugin for visualizing and editing of xmiCAS files and therefore it is an alternative for the CAS Editor. However, the TextMarker projects are now only using the CAS editor and the CEV plugin is abandoned. Move this plugin to the other sandbox projects (e.g., CasViewerEclipsePlugin) in order to archive it.