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.tests/test/org/eclipse/birt/data/engine/api/APITestCase.java
protected abstract DataSourceInfo getDataSourceInfo( );
	
	/**
	 * Wrap the info for the preparation of data source, when derby is used, it
	 * needs to provide the createSql and dataFileName to create a table for
	 * test.
	 */
	public class DataSourceInfo
	{
		private String tableName;
		private String createSql;
		private String dataFileName;
		/**
		 * @param tableName, used table name
		 * @param createSql, sql to create table
		 * @param dataFileName, data to insert table
		 */
		public DataSourceInfo( String tableName, String createSql,
				String dataFileName )
		{
			this.tableName = tableName;
			this.createSql = createSql;
			this.dataFileName = dataFileName;
		}
	}
	
	/**
	 * @throws Exception
	 */
	protected void closeDataSource( ) throws Exception