v0.7 xengine:
1.improve "series" module, especially the implementation of XBaseSerialMgr.java
2.change the construction of "image.loader" module.
2.1 add Interface XImageLoader, XImageLocalLoader, XImageRemoteLoader, XScrollLazyLoading
2.2 "local loader" is responsible for loading local image(from memory or sd card), including XImageViewLocalLoader, XImageSwitcherLoacalLoader
2.3 "remote loader" is responsible for loading and downloading(if not exisit).including XImageViewRemoteLoader
2.4 "scroll" responsible for the feature of lazy loading.including XScrollLocalLoader, XScrollRemoteLoader