Fix Multicuror Multiline Paste

[pjkaufman]

Fixes #480

Change Made:

• Made sure to account for the scenario where there are multiple cursors by going ahead and breaking the clipboard text into multiple different paste values if it has a line count that is an exact multiple of the amount of cursors, otherwise it just pastes the same text to all of the multiple cursors
• Added documentation around this limitation

There is a possible issue where you copy the same amount of lines that you would like to have it pasted as (i.e. copy two lines then enter multicursor mode and want to paste it in 2 places, but I am not sure how I would know that on my end).