Adds default value support for linked items & asset elements (fixes https://github.com/kontent-ai/management-sdk-js/issues/84), updates default property signature (bd13ec2)
Removes 'codename' property from snippet element data as it is not supported (fixes https://github.com/kontent-ai/management-sdk-js/issues/83) (861c88f)
Fixes 'uploadAssetFromUrl ' method from never resolving by cloning config and making sure proper headers are used for 'addAsset' method (fixes https://github.com/kontent-ai/management-sdk-js/issues/82) (c12fa3c)