Update CHANGLOG to reflect recent changes

Ready for version 0.2.0.
Depend on vCloud Core version 0.6.0

Necessary because of the changes to
`Vcloud::Core::Vm::configure_guest_customization_section`.
Version 0.2.0

Minor version bump because these changes break backwards compatibility
but we're not yet at version 1.0 so our API should be considered
unstable.
Merge pull request #53 from gds-operations/update-changelog

[#74382904] Update CHANGELOG and release version 0.2.0