Fix when recreating Workspace type in Studio, easyshare type not proposed

When recreating Workspace type and defining children types in Studio, the public easyshare document type is not offered as a child.

To reproduce:

• take an empty Nuxeo installation and deploy nuxeo-jsf-ui and easyshare addons
• boot Nuxeo and create a workspace and create document => You are proposed the easyshare public share type : so far so good.

• take a Studio project that recreates the Workspace type and defines the types of children documents => deploy that project and create a workspace and create document => You are not proposed the easyshare public share type : this is the issue.

Issue: There is no way in Studio out of the box to add the public share type.
Request: when redefining the Workspace in Studio, still being able to create the easyshare public share folder in the GUI