EDIT

I tried to update from TaxEditor version 4.7 to version 4.8 but the update stopped in the middle without the following error message:

!ENTRY org.eclipse.equinox.p2.engine 4 4 2017-08-02 10:30:08.933
!MESSAGE An error occurred while collecting items to be installed
!SUBENTRY 1 org.eclipse.equinox.p2.engine 4 0 2017-08-02 10:30:08.933
!MESSAGE session context was:(profile=DefaultProfile, phase=org.eclipse.equinox.internal.p2.engine.phases.Collect, operand=, action=).
!SUBENTRY 1 org.eclipse.equinox.p2.transport.ecf 4 1200 2017-08-02 10:30:08.933
!MESSAGE Artifact not found: http://cybertaxonomy.eu/download/taxeditor/update/nightly/plugins/org.eclipse.nebula.widgets.compositetable_1.0.0.201706221838.jar.
!STACK 0
java.io.FileNotFoundException: http://cybertaxonomy.eu/download/taxeditor/update/nightly/plugins/org.eclipse.nebula.widgets.compositetable_1.0.0.201706221838.jar
    at org.eclipse.equinox.internal.p2.transport.ecf.RepositoryStatusHelper.checkFileNotFound(RepositoryStatusHelper.java:297)
    at org.eclipse.equinox.internal.p2.transport.ecf.FileReader.checkException(FileReader.java:480)
    at org.eclipse.equinox.internal.p2.transport.ecf.FileReader.sendRetrieveRequest(FileReader.java:437)
    at org.eclipse.equinox.internal.p2.transport.ecf.FileReader.readInto(FileReader.java:360)
    at org.eclipse.equinox.internal.p2.transport.ecf.RepositoryTransport.download(RepositoryTransport.java:101)
    at org.eclipse.equinox.internal.p2.transport.ecf.RepositoryTransport.download(RepositoryTransport.java:156)
    at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.downloadArtifact(SimpleArtifactRepository.java:669)
    at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.downloadArtifact(SimpleArtifactRepository.java:591)
    at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.getArtifact(SimpleArtifactRepository.java:723)
    at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.getArtifact(MirrorRequest.java:319)
    at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.transferSingle(MirrorRequest.java:288)
    at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.transfer(MirrorRequest.java:223)
    at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.perform(MirrorRequest.java:153)
    at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.getArtifact(SimpleArtifactRepository.java:707)
    at org.eclipse.equinox.internal.p2.artifact.repository.simple.DownloadJob.run(DownloadJob.java:63)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

It seems like there is something wrong with the dependency to the nebula widgets