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
{
			assert dataFile != null;
			assert metaFile != null;
			this.dataFile = dataFile;
			this.metaFile = metaFile;
			
			this.init( );
		}
		/**
		 * Initialize the properties of a MergeUtil instance
		 * 
		 * @throws DataException
		 */
		private void init( ) throws DataException
		{
			try
			{
				FileInputStream fis = new FileInputStream( metaFile );
				BufferedInputStream bis = new BufferedInputStream( fis );
				rowCount = IOUtil.readInt( bis );
				rsClass = new ResultClass( bis );
				bis.close( );
				fis.close( );
			}
			catch ( FileNotFoundException e )
			{
				throw new DataException( ResourceConstants.DATASETCACHE_LOAD_ERROR,
						e );
			}
			catch ( IOException e )