Use JSON import for environment variables

Use JSON import for environment variables

The env can be provided as a JSON list `[{"name": "PORT", "value": "8080"}]`.
The `dict2items` filter provided by ansible is _almost_ what we want, but it
keeps the value original types (a boolean is kept as a boolean in the JSON value).
Since environment variables are strings and `clever-tools` does not want to make
the implicit coercion for us, we need to do it ourselves.