Add optional automations, configurable by context menu per annotation

[Earthwings]

• auto-fit box after time changes: adjusts box size to nearby points during prediction when time changes. Disabled by default.
• shrink box to points after resizing: after the user adjusts the box size, it is automatically shrinked to fit the points inside but not more (but a margin). Enabled by default.
• shrink box to points before committing: similar to above, but called when the user commits an annotation. Enabled by default.