Possible enhancement: Add scopedVars that points to bucket timestamp

Hi there, and thanks for this excellent plugin.

I wolud to suggest a possible enhancement to use the bucket timestamp (when event occurred) in tooltip and in particular in URL item. This is my working scenario. When i click on status map bucket i want to open another dashboard that starts at bucket time.

I tried with __from, __to (or _url_time_range) but seems taht these values refer to dashboard time and no to bucket time.

So i tried to add this after line 221in tooltip.js

scopedVars["__date_from"] = { value: timestamp //defined at line 153 };

and now i can open the new dashboard starting from event occured.

[diafour]

__bucket_from and __bucket_to are available in 0.5.0.

[diafour]

@dmalanaphy There is a pull request #222 which implements an expanded range for __bucket_from and __bucket_to. Please, comment there what you think.