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/executor/DataSetCacheManager.java
{
		if ( needsToCache( dataSetDesign, cacheOption, alwaysCacheRowCount ) == false )
			return false;
		return cacheMapManager.doesSaveToCache( DataSourceAndDataSet.newInstance( this.dataSourceDesign,
				this.dataSetDesign,
				this.parameterHints ) );
	}
	/**
	 * @return
	 */
	public boolean doesLikeToCache( )
	{
		return needsToCache( dataSetDesign, cacheOption, alwaysCacheRowCount );
	}
	/**
	 * @param dataSourceDesign
	 * @param dataSetDesign
	 * @param parameterBindings
	 * @param cacheOption
	 * @param alwaysCacheRowCount
	 * @return
	 */
	public boolean doesLoadFromCache( IBaseDataSourceDesign dataSourceDesign,
			IBaseDataSetDesign dataSetDesign,
			Collection parameterHints, Map appContext, int cacheOption, int alwaysCacheRowCount )
	{
		if ( needsToCache( dataSetDesign, cacheOption, alwaysCacheRowCount ) == false )
			return false;
		
		this.setDataSourceAndDataSet( dataSourceDesign,