Revert "EDM Mode: add symbol number as property of symbol widget"

This reverts commit 88877d24d23f2c8c76e01cd2baac7768904642c4.

Conflicts:

	products/DLS/plugins/org.csstudio.opibuilder.widgets.edm/src/org/csstudio/opibuilder/widgets/edm/editparts/EdmSymbolEditpart.java