Changes

Updated target platform, baseline, and all versions for 3.20.0
developments

Relax demands on PaletteContainer addAll Methods.

In the last clean-up a non back-wardscompaptible interface change was
introduced. This commit fixes that.

Use PrecisionPoint instead of Point to handle deprecation warning

This commit partially reverts fd75841fd7e0638c18827f203257e504536fb15e
and uses PrecisionPoints instead of Points in the FanRouter class, to
store the bend point.

Note that because the mid point is a plain point, the equality check is
done using the integer coordinates.

Resolves #383