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/i18n/ResourceConstants.java
public final static String GROUP_NOT_EXIST = "data.engine.GroupNotExist";
	public final static String INVALID_SORT_EXPR = "data.engine.BadSortKeyExpr";
	public final static String PARAMETER_METADATA_NOT_SUPPORTED = "data.engine.NoParamMetaForDataSource";
	public final static String UNEXPECTED_ERROR = "data.engine.UnexpectedError";
	public final static String CANNOT_CONVERT_PARAMETER_TYPE = "data.engine.ConvertDataTypeError";
	public static final String CANNOT_INSTANTIATE_AGGREGATION_FACTORY = "data.engine.CannotInstantiateAggregationFactory";
	public static final String DUPLICATE_AGGREGATION_NAME = "date.engine.DuplicateAggregationName";
	public static final String INCORRECT_GROUP_KEY_VALUES = "data.engine.incorrectGroupKeyValues";
	public static final String NO_EXPRESSION_PROCESSOR_AVAILABLE = "data.engine.NoExpressionProcessorAvailable";
	public static final String INCONVERTIBLE_DATATYPE="data.engine.InconvertibleDatatype";
	public static final String CONVERT_TO_DATATYPE_ERROR="data.engine.ConvertToDataTypeError";
	public static final String NO_ROW_UPDATE="data.engine.NoRowUpdate";
	public static final String BAD_DATA_TYPE= "data.engine.BadDataType";
	public static final String BAD_DATA_EXPRESSION="data.engine.BadDataExpression";
	
	public static final String CACHE_FUNCTION_WRONG_MODE="data.engine.cacheFunctionWrongMode";
	public static final String INDEX_ARRAY_INVALID="data.engine.document.invalidIndexArray";
	public static final String GROUP_ITEM_INCORRECT="data.engine.document.invalidGroupItem";
	public static final String RESULTITERATOR_NOT_OPEN="data.engine.resultIteratorNotOpen";
	public static final String RESULTITERATOR_CLOSED="data.engine.resultIteratorClosed";
	public static final String INVALID_OUTPUT_PARAMETER_INDEX="data.engine.invalidOutputParameterIndex";
	public static final String OUTPUT_PARAMETER_OUT_OF_BOUND="data.engine.outputParameterOutOfBound";
	public static final String INVALID_OUTPUT_PARAMETER_NAME="data.engine.invalidOutputParameterName";
	public static final String NOT_SUPPORT_IN_PRESENTATION="data.engine.document.notSupportInPresentation";
	public static final String WRONG_STATUS="data.engine.wrongStatus";
	public static final String WRONG_VERSION="data.engine.wrongVersion";
	public static final String UNSUPPORT_OPERATION_EXCEPTION="data.engine.unsupportOperationException";
	public final static String POSSIBLE_MIXED_DATA_TYPE_IN_COLUMN = "data.engine.possibleMixedDataTypeInColumn";
	public static final String RESULT_CLASS_SAVE_ERROR="data.engine.resultClassSaveError";