Add Box Input

[anuragxel]

Add ability to provide box input along with point input (with nice looking mousedown animation). Though I'm not sure if it's needed to be honest, point input works really well in general.

[yogendra-yatnalkar]

Hey sorry, did not get time to contribute in terms of code until this point. In future the box input will be required as a feature.

Reason: I had worked on a use-case where images were very wide, and the segmentation map was also very wide. I had to segment the LED ad-board. Example:

So, if you observe, we have multiple objects in between. If we just provide a single point input, it might not identify the entire board, hence I believe the BB will be required in such cases.

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On a side note: The tagging tool is awesome.