[425568] CSV export must not export cropped label

When a cell belongs to a column defined by a FeatureColumnMapping with
an empty label computation expression, the item property descriptor is
used to compute the DCell label to display (see:
org.eclipse.sirius.table.business.internal.refresh.DTableElementSynchronizerSpec.setLabelWithFeatureValue(DCell,
ColumnMapping, String) when there is no label expression)

For non Boolean and non EEnum data types,
org.eclipse.emf.edit.provider.ItemPropertyDescriptor.ItemDelegator.convert(EDataType,
Object) crops the obtained value at the first found char on which
Character.isISOControl return true and add "..." at the end of the
cropped label.

The displayed label in DCell and semantic property view tab is the
cropped label, the complete label is displayed during direct edit. 

The CSV export and html export now use the complete semantic value and
not the cropped label.

Change-Id: I7913c11c1bcffb728a621acab8b5d084a9fdeeb9
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>