Closes #640

Fixes #653

Fixes #635

Merge as much as possible stuff from second loop to first. Use second
only to set width and X for ports.

More folding
Clean some magic height changes. Bottom space now consists of
max(port_spacing, port_spacingT) + border width - trailing port_spacing.
Port types are traversed in loop, using array.

First stage of refactoring.
Fixed indentation of line, added in visual correction of lineHinting
effect.

Use single rect through all drawing sequence (change of decrement in one
place affects all next steps).

By shifting border inside of logical bound, free space around is
increased by one line weight.

Same as for main canvas - 2d cursor is aligned to pixels. Visible
difference is different look of antialiased map itself.

Current implementation fills outest pixels incompletely, making slightly
blured look.

When box is moved in scaled state, coordinates get random fraction,
which breaks border-to-pixel alignment.

Make border's outer edge aligned to pixel margin

Mouse buttons in nix world have numbers 1..3 for 3 primary buttons, but
qt has special meaning for numbered names, using symbolics for first
standard buttons.

Simple click removes connections, which are too close to pointer
(for now 1px, but would be nice to make configurable).
Dragging cuts all connections on the way.

Fixes #616