Add support to Interface based model

[handreyrc]

Issue#194

This PR intoduces interfaces to model definitions allowing to work with plain objects instead of class instances.
This approach makes it easier handling changes in the model and make it compatible with libs such as immer.

The idea behind this implementation is to keep classes under the hood to handle model properties, however, only plain objects are exposed by unmarshalling JSON/YAML or by using the SKD builders. To achieve that, lodash lib was used to convert class instances to plain shallow copies of the original class instances and so preserving properties and methods.

No changes in the API were be introduced by this PR.
Old and deprecated dependencies of the project were updated.
Immer dependency is only being consumed by in the unit tests.

[ricardozanini]

My only concern is with the changes you made to the schema. Why were they necessary? The rest seems pretty straightforward to me.

[handreyrc]

@ricardozanini,

The changes to the schema were made automatically by the script "update-code-base". That was the first thing I did before start working on the project.
It donwloads the schemas, then it recreates definitions (this is an intermediate step, the actual definitions exposed by the sdk are not auto-generated) and builders based on the downloded schemas.

Please, @ricardozanini @JBBianchi, let me know if it is an issue.
If so, I can port my changes on top of the orignal code and run the script recreate the builders only. It's not a big deal.

Thanks a lot!

[handreyrc]

@ricardozanini,
Just adding more information about the schema. The script I mentioned above is downloading the schema from this URL:
https://raw.githubusercontent.com/serverlessworkflow/specification/0.8.x/schema/workflow.json

[ricardozanini]

@JBBianchi is on PTO until next week; we will hold this PR until then.