reconstruct the implementation of API in assetManage.js
design the API of assetManagement
design the API of direcotry tree
Add API for asset manage
reconstruct asset model and some API implementation
design and implement asset directory tree
add GeoViewerWin to display geometry and take snapshot
list assets in assetsWin
add transform control for GeoViewerWin
add name editing capability to GeoViewerWin.js
add searchAssets capability
make assets pickable
add capability of import assets from server
fix bug of function checkModified in revisionControl.js
fix bugs