Gaphas

Changes

* Add horizontal scrolling with `Shift`+`ScrollWheel`.

Changes

- Integrate line segments, `segment_tool` is history (380)
- `gaphas.connector` is split in `gaphas.handle` and `gaphas.port`
- Moved `gaphas.aspect module` to `gaphas` package
- Moved `gaphas.view.model` to `gaphas` package

This cleanup should reduce the chance of requiring GTK, which is a huge benefit for, for example, the Sphinx extension in Gaphor.

Changes

* Fix disconnect issue

Changes

* `gaphas.GtkView` has been removed. Import `GtkView` from `gaphas.view` instead.
* Move selection code to `gaphas.selection`
* Make most code *not* depend on GTK (explicit or implicit)
* Handles change color when glued to another item
* Improve usability of guides by increasing the glue margin to 4 pixels. the margin can now also be configured.
* Glueing takes into account all items at a specific position (was only the top-most). `item_at_point` returns an iterator.
* The `CairoContext` protocol has been removed

Fixes

* Fix errors with tuple/Position comparison

Changes

- Remove JuggleError amolenaar (367)
- Fix issue where horizontal line could not be overridden in Gaphor

Changes

* Allow `Line.horizontal` to be overwritten.
* Documentation fixes