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/executor/cache/ResultObjectUtil.java
* Contruction, private 
	 */
	private ResultObjectUtil( )
	{
	}
	
	/**
	 * New a instance of ResultObject according to the parameter of object array
	 * plus the metadata stored before.
	 * 
	 * @param ob
	 * @return RowData
	 */
	public ResultObject newResultObject( Object[] rowData )
	{
		return new ResultObject( rsMetaData, rowData );
	}
	/**
	 * Deserialze result object array from input stream. The reading procedure
	 * is strictly sequential, that means there is no random access.
	 * 
	 * Datatype Corresponds to executor#setDataType
	 * 
	 * @param br
	 *            input stream
	 * @param length
	 *            how many objects needs to be read
	 * @return result object array
	 * @throws IOException
	 */