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/api/DataEngineContext.java
* @return cacheCount
	 */
	public int getCacheOption( )
	{
		return this.cacheOption;
	}
	
	/**
	 * @return cacheCount
	 */
	public int getCacheCount( )
	{
		return this.cacheCount;
	}
	/**
	 * This method is used to set the cache option for current data engine
	 * instance. These option values will override the values defined in
	 * individual data set and its application context. The option value has
	 * three posible values, CACHE_USE_DEFAULT, CACHE_USE_DISABLE,
	 * CACHE_USE_ALWAYS. The cacheCount values can be larger than 0, which
	 * indicates the count of how many rows will be ccached, equal to 0, which
	 * indicates cache will not be used, less than 0, which indicates the entire
	 * data set will be cached.
	 * 
	 * Please notice, this cache function only available for
	 * DIRECT_PRESENTATION. In other cases, exception will be thrown.
	 * 
	 * @param option
	 * @param cacheCount
	 */