Optimize widget info dialog to show archived status

[shroffk]

There are a few improvements suggested in #3387 which should be incorporated in the info dialog.

[georgweiss]

@shroffk, can you please clarify?

[shroffk]

I am thinking primarily of finding a way to batch the queries.
While AA supports this... I am not sure how to do this via the archive:// datasource

we can also have the datasource return more interesting connection information which could make the column more useful... in addition to yes/no we can have last timestamp, currently connected, etc... again I am not sure how to do all of this but we can start with a list of additional meta data that would make this flag more useful.

[georgweiss]

@shroffk, how about adding a column showing timestamp of the VType object received from archiver data source. I know this could "intentionally" be a fair amount of time in the past, but if the time stamp is very recent it would indicate that the PV is being actively archived.

As for batch requests and a new type of data source... In my understanding data sources deal with VType objects, so a new type of data source would maybe need to return a VTable containing columns for the metadata. The input object for such a data source would of course be an array of PV names.