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 UNDEFINED_DATA_SOURCE = "data.engine.UndefinedDataSource";
	public final static String UNDEFINED_DATA_SET = "data.engine.UndefinedDataSet";
	public final static String UNSUPPORTED_DATASOURCE_TYPE = "data.engine.UnsupportedDataSourceType";
	public final static String UNSUPPORTED_DATASET_TYPE = "data.engine.UnsupportedDataSetType";
	public final static String UNSUPPORTED_GROUP_ON_BLOBAndCLOB ="data.engine.UnsupportedGroupOnClobAndBLOB";
	public final static String UNSUPPORTED_SORT_ON_BLOBAndCLOB ="data.engine.UnsupportedSortOnClobAndBLOB";
	public final static String UNSUPPORTED_DIRECT_NESTED_AGGREGATE="data.engine.UnsupportedDirectNestedAggregate";
	public final static String NOT_END_GROUP  = "data.engine.EndOfGroupOnly";
	public final static String INVALID_AGGR_GROUP_LEVEL  = "data.engine.InvalidAggrGroup";
	public final static String INVALID_AGGR_PARAMETER  = "data.engine.WrongNumAggrArgs";
	public final static String INVALID_AGGR_GROUP_EXPRESSION ="data.engine.InvalidAggrGroupExpression";
	public final static String DUPLICATE_PROPERTY_NAME = "data.engine.DupPropertyName";
	public final static String SUBQUERY_NOT_FOUND = "data.engine.NoSubQueryName";
	public final static String MISSING_DATASOURCE_EXT_ID = "data.engine.DataSourceMissingExtId";
	public final static String STARTING_GROUP_VALUE_CANNOT_BE_NULL = "data.engine.NullGroupStart";
	
	public final static String RESULT_CLOSED = "data.engine.ResultClosed";
	public final static String NO_CURRENT_ROW = "data.engine.NoCurrentRow";
	public final static String INVALID_JS_EXPR = "data.engine.InvalidJSExpr";