Bug 180189 Support in memory data set cache.
Currently, Design-Time Data Cache is stored on disks. By performance tests using ramdisk, we found that caching in physical memory can improve the performance of RunAndRender by 30%.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/DataSetCacheUtil.java
{
	/**
	 * @param context
	 * @param appContext
	 * @return
	 */
	public static int getCacheOption( DataEngineContext context, Map appContext )
	{
		int cacheOption = context.getCacheOption( );
		
		if ( appContext != null )
		{
			Object option = appContext.get( DataEngine.DATA_SET_CACHE_ROW_LIMIT );
			if( option != null )
			{
				int rowLimit = getIntValueFromString(option);
				if( rowLimit == 0 )
				{
					return DataEngineContext.CACHE_USE_DISABLE;
				}
				else
				{
					return DataEngineContext.CACHE_USE_ALWAYS;