* Find minimum start block number
* Perform fill if db is empty
* Make getStartBlock method public in GraphWatcher
* Use dataSources property
* Update server template to fill block on start
* Avoid passing graphWatcher from generated watcher
* Ensure block filling for non-subgraph watchers as well
* Remove getStartBlock method from GraphWatcher
* Remove graphWatcher property from ServerCmd
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Co-authored-by: neeraj <neeraj.rtly@gmail.com>