Lots of small fixes for the Simantics SDK build

* org.apache.batik/1.8.0 is taken from external-components/manual now.
  Removed it from this repository.
* org.simantics.sdk now includes plenty of previously missing plug-ins
and features: org.simantics.help.*,
org.simantics.spreadsheet.fileimport, org.apache.pdfbox*,
org.simantics.tests.modelled*, org.simantics.diagram.svg,
org.simantics.browsing.ui.nattable*
* many build.properties fixes, e.g. removal of non-existent files and
addition of missing binary/source artifacts
* added new feature org.simantics.help.addons to bundle together all the
recently added org.simantics.help.* plug-ins for modelled help page
construction in the Simantics Desktop workbench.
* added new feature org.simantics.browsing.ui.nattable.feature to gather
together org.simantics.browsing.ui.nattable and its external component
dependencies (nattable.core, fastutil)
refs #6621

Change-Id: I203c1fac381325d59925e19e26ee338db7ff9852