Move text respecting lines as `kill-rectangle` and `yank-rectangle` do

[shackra]

When users enter rectangle-mark-mode, move-text should respect text layout around the region marked.

[shackra]

edge case:

pdftotext screw these columns of text from the PDF I converted, selecting a rectangle, killing the text and yanking it in its correct place works, but sometimes you have to add spaces to match column alignment before yanking.

move-text seems to move the entire line of the rectangle region marked, carrying the white spaces on those lines with the marked rectangle.

[jasonm23]

A PR to solve this would be very welcome.