Merge pull request #792 from SpineEventEngine/release-base-1.9.0

Release 1.9.0

Merge pull request #719 from SpineEventEngine/release-1.8.2

Release 1.8.2

Merge pull request #702 from SpineEventEngine/release-1.8.0

Release 1.8.0

The latest stable revision with version 1.x.

Later revisions have version 2.x and are not backwards compatible with this revision.

Merge pull request #610 from SpineEventEngine/update-copyright-2021-p…

…art2

Update copyright to 2021 (part 2)`

Merge pull request #600 from SpineEventEngine/release/v1.7.0

Release v1.7.0

Merge pull request #565 from SpineEventEngine/release-1.6.0

Release `1.6.0`

Merge pull request #517 from SpineEventEngine/release-1.5.0

Release 1.5.0

Merge pull request #500 from SpineEventEngine/release-1.3.0

Release `1.3.0`

Merge pull request #494 from SpineEventEngine/entity-state-marker-int…

…erface

`EntityState` marker interface