Bug 177870 Allow design-time data set cache to be controlled solely by AppContext
This is to request that BIRT allows data set caches to be controllable solely by runtime parameters/settings, without the application having to update the report design to set data set cache preferences. Since BIRT DataEngine already reads request Application Context to determine if data set cache should be disabled, we will expand AppContext to allow the application to enable data set cache and to set max row count. The following new application context key will be introduced: org.eclipse.birt.data.cache.RowLimit The value of this app context is expected to be an integer. Its value can be: 0: Disable data set cache regardless of report design settings and DataEngineContext settings. Positive integer: Enable data set cache. This row limit will be used for ALL data sets, regardless of settings on individual data set designs. If this key is absent in the appcontext, or if its value is not a non-negative integer (including NULL), we will following current rules to determine cache settings. As part of this change, we will also deprecate existing app context key "org.eclipse.birt.data.engine.dataset.cache.option". Its declaration in DataEngine class should be marked deprecated. We will continue to read and handle its value, but the user is encouraged to use the new key "org.eclipse.birt.data.cache.RowLimit" (by setting its value to 0).
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/PreparedDataSourceQuery.java
{
		return this;
	}
	
	/**
	 * Executes the prepared execution plan.  This returns
	 * a QueryResult object at a state ready to return its 
	 * current result iterator, or evaluate an aggregate expression.
	 * <p>
	 * This includes setup runtime state, and evaluation of
	 * any beforeOpen and afterOpen scripts on a data set. 
	 * @return The QueryResults object opened and ready to return
	 * 		the results of a report query. 
	 */
	public IQueryResults execute( Scriptable scope ) throws DataException
	{
		return this.execute( null, scope );
	}
	/**
	 * Executes the prepared execution plan as an inner query that appears
	 * within the scope of another report query. The outer query must have been
	 * prepared and executed, and its results given as a parameter to this
	 * method.
	 * 
	 * @param outerResults
	 *            QueryResults for the executed outer query
	 * @return The QueryResults object opened and ready to return the results of
	 *         a report query.
	 */
	public IQueryResults execute( IQueryResults outerResults, Scriptable scope )