OPT: make pandas (and may be scipy, ... anything else?) dependency optional#1282

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yarikoptic wants to merge 3 commits intoNeurodataWithoutBorders:devfrom

yarikoptic:opt-pandas

Commits on Aug 13, 2020

OPT: defer import of pandas in core.py until its explicitly asked for need/use
yarikoptic
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OPT: remove pandas from requirements
yarikoptic
committed
OPT(+TODO): delay import of pandas only if DataFrame could be actually passed into
yarikoptic
committed