Feature Request: Manually Sort Datasets

[billdenney]

As described in #37, in a few scenarios-- especially when drawing lines between data-- it would be helpful to be able to manually sort the dataset.

Currently, automatic sort is enabled when in the "View Data" window, but there doesn't appear to be a way to manually sort the data as may be useful for hysteresis plots.

By the way, I'll accept it if you think this is too-niche and that if you want data sorted in a specific order, you have to enter it in that order.