Bug 73083 [Encoding] Need to verify encodings and indicate unavailable ones
When the encodings are set up we need to ensure that they are in the list of valid encodings available from the VM. Those that are not should be indicated as such and not be selectable in the UI.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/dialogs/AbstractEncodingFieldEditor.java
* @param parent
	 */
	public AbstractEncodingFieldEditor(String name, String labelText, Composite parent) {
		super(name, labelText, parent);
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.preference.FieldEditor#adjustForNumColumns(int)
	 */
	protected void adjustForNumColumns(int numColumns) {
		((GridData) getContainer().getLayoutData()).horizontalSpan = numColumns;
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.preference.FieldEditor#doFillIntoGrid(org.eclipse.swt.widgets.Composite, int)
	 */
	protected void doFillIntoGrid(Composite parent, int numColumns) {
		container = createEncodingGroup(parent, numColumns);
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.preference.FieldEditor#doLoad()
	 */
	protected void doLoad() {
		if (encodingCombo != null) {
			List encodings = IDEEncoding.getIDEEncodings();
			String resourcePreference = getStoredValue();
			populateEncodingsCombo(encodings, resourcePreference);
			updateEncodingState(resourcePreference == null || resourcePreference.equals(defaultEnc));
		}
	}
	/**
	 * Get the value that is current stored for the encoding.