Snapshot for dashboard

[jingyugao]

Sometimes，the data will change, when dashbord is freshed, everything will changed too.
If we want to save the current dashbord data , we need export each query's result and make a screenshot of visualize.
This is very cumbersome.
How about save all the data of current dashbord to disk(or oss), and if we need to see history data, we just restore dashbord from disk data.