Include org.apache.poi.feature in org.simantics.spreadsheet feature.

Include org.apache.poi.feature in org.simantics.spreadsheet feature.

This replaces the inclusion of only the org.apache.poi plug-in which
does not include all the dependencies required by Apache POI.

Also, exclude source org.apache.poi[.feature] source bundles from build.
Since there is no source bundle for org.apache.poi 3.15.0 so we must
exclude it from the build to get the build to pass.

refs #6813

Change-Id: Id5f388596c73f1ec58f93c884ad630e40f74d24c