Added colors in the statistics screen for pregrade and invalid units.

Added in coloring for pregrade, grade and invalid words in statistics
screen
Added a pullup legend in statistics screen with a grippy on the bottom
of the screen showing all the colors with a popup explaining the
meaning.
Added options in the configuration to select the colors.

BUG:338244
BUG:338245
FIXED-IN: 4.14.1