Replace zap with zerolog.
zerolog has a cleaner interface and can be easily configured with custom
error chain printing using a new error handling library that will be
implemented in another PR.
Replace https://github.com/satori/go.uuid with maintained version at
https://github.com/gofrs/uuid
Since the new version uuid.NewV4 returns an error when failing to read
from the random source reader we use uuid.Must to panic on error since
it's considered an unrecoverable error.
In future, if needed, we could handle the error instead of panicking.
Handle `.agola/config.star` files in starlark config format.
To provide a context like done for jsonnet we require that the starlark agola
config file contains a main function that will receive a config context as a
dict.
We also had to implement our own json conversion from a starlark dict since go
starlark removed its own function.
Just a raw replace of "github.com/pkg/errors".
Next steps will improve errors (like remote errors, api errors, not exist errors
etc...) to leverage its functionalities
Handle config files with name `config.jsonnet`, `config.json` and
`config.yml` and take the first from the repository in this order
For a jsonnet file execute it and use the generated output as the config
