Add migration to capture new help text on 1000g and EVS concepts

Fix #103.

This new text is meant to clear up any confusion when entering
percentages in the range controls. The percentages should be entered as
values in the range [0.0, 1.0] but this was not clear before. This is
now spelled out in the help text with an example.

Signed-off-by: Don Naegely <naegelyd@gmail.com>