upgrade solutions for Transform service => Convert service

TransformServiceCommon will be replaced with ConversionService.

I assume that we deprecate TransformServiceCommon and remove the Implementation.
But we have to uses cases to provide :

1 - make all transformers run as converters
Most of the built-in transformers can be easily migrated to the new API.
But for addons and external contributions, we want a painless way : provide a way to run a transformer written with the old API run via the new ConversionService API.
For that we just need to provide a generic converter that will know how to run a Transformer.
We will probably need to modify Nuxeo Runtime to redirect the contributions to TransformService component to a compat component that will do the registration of the compat plugins to the ConversionService.

2 - provide compatibility for the code using the TransformServiceCommon API
Nuxeo's code will be migrated to the new API.
For other code we may provide a simple Wrapper service that runs unboxed CompatConverters via the old API.