Implemented: in cons mode, when dragging, then place the effect frame
such that the cursor is centralized location-wise within the effect
frame.

Implemented also: don't remove target frame and effect frame until the
actual effect has been performed (or has started at least). This goes in
general for modes.

Signed-off-by: Jakob Brandsborg Ehmsen <jakobehmsen.github@gmail.com>