Fix T61591 Bevel tool not executing on mouseup.

When modal map was introduced, left out handling of what
happens when bevel is made active tool in toolbar and user
starts bevel by clicking and dragging.

Bevel: remove workspace text message when exiting bevel.

The message with shortcuts was hanging around after bevel
exited.

Bevel: fix twist on bevel of cylinder with >= 200 sides.

This triggered an "almost parallel" case in setting the
offset meet points, which is OK but code needed improvement
put the meet point in a more accurate place.
This ia fix for part of the report T61214.

Fix T61427: Bevel crash with patch miter.

The adjustment phase had broken assumptions after adding miters,
and sent a null problem to eigen. Fixed code to check assumptions.

Bevel: Make modal keymap instead of hardcoded.

Also added keys for toggling harden normals,
and cycling through miter types.
Still to do: add some shortcuts for affecting the
spread value for arc miters.

Bevel, fix crash when adjust offsets with inner arc miter.

Previous assumptions about boundary verts always being attached
to edges are now false.

Bevel: fix regression re even adjustment of offsets.

Mistakenly had left a debugging assignment that disabled
the offset pass. This commit re-enables it.

Bevel: better attachment points for unbeveled edges, arc miter.

Bevel - better corner shapes for inner arc miters.

The subdivision method for getting corner shapes has a fullness
parameter which had been set by eye before. This change uses fullness
as found by offline search process to best match the superellipsoid
octant in the cube corner case (except cube corner case is still handled
by other code). This somewhat improves the look of cube corners with
inner arc miters, however.

Fix bevel modifier spread value bug.

Was using same field as value, by mistake.