reduce overhead index requests

[shanghaikid]

This pr will reduce the problem described in #338 by

1. build another getCollectionInfo api to get collection info without index info which is slower to call.
2. rename getCollection api to getCollectionWithIndexInfo.
3. if no index info is required, replace getCollection with getCollectionInfo in the page.
4. upgrade package lru-cache to the latest version
5. use a cache for describeIndex, will delete cache if create/drop the index.
6. support clearCache, if user clicks the refresh button on collection list page.