Update documentation to reflect Toolbox v0.8

[jkiviluo]

Both documentation and examples should be updated

• objects and relationship need to change to entities
• is_active changed to entity_alternative

[datejada]

@jkiviluo @nhniina will review the timeline for version 0.9. Depending on this timeline, we can continue this issue in two ways:

1. Wait for 0.9, and in the meantime, add a warning at the beginning of the tutorials that they are in the old version of SpineToolbox
2. Update them now to version 0.8, and once version 0.9 is ready, we update again (might be a marginal update)

[jkiviluo]

Toolbox v0.9 will not bring big structural changes affecting the user. There may be visual changes (so image snapshots may become bit outdated), but I think it's fine to do these updates already if someone has the time.