Bug 180842 Config memory buffer size in data engine execution.
To tuning the performance, it is necessary for DtE to expose API for clients to config the size of memory it used to store the final result set. A new AppContext string, "org.eclipse.birt.data.cache.memory.size" is proposed. The new appcontext entry only accept positive integer as input, the unit of which would be MB.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/document/viewing/DummyEventHandler.java
* @see org.eclipse.birt.data.engine.odi.IEventHandler#handleEndOfDataSetProcess(org.eclipse.birt.data.engine.odi.IResultIterator)
	 */
	public void handleEndOfDataSetProcess( IResultIterator resultIterator )
	{
	}
	/*
	 * @see org.eclipse.birt.data.engine.odi.IEventHandler#getValue(org.eclipse.birt.data.engine.odi.IResultObject,
	 *      int, java.lang.String)
	 */
	public Object getValue( IResultObject rsObject, int index, String name )
			throws DataException
	{
		return rsObject.getFieldValue( index );
	}
	/*
	 * @see org.eclipse.birt.data.engine.odi.IEventHandler#isRowID(int,
	 *      java.lang.String)
	 */
	public boolean isRowID( int index, String columnName )
	{
		return false;
	}
	/*
	 * @see org.eclipse.birt.data.engine.odi.IEventHandler#getBaseExpr(java.lang.String)
	 */
	public IBaseExpression getBaseExpr( String name )
	{
		return null;
	}
	/*