Installer must know that cap = server + jsf-ui

The installer must know that if a package requests cap, it can be satisfied with a server + jsf-ui package.

An empty package nuxeo-jsf-ui for target platform cap-8.3 and cap-8.3-SNAPSHOT has been deployed (https://connect.nuxeo.com/nuxeo/site/marketplace/package/nuxeo-jsf-ui?version=8.3.0-cap).

In addition, the installer code has been changed so that when a package for target platform cap is read, we also add the target platform server and the dependency nuxeo-jsf-ui. This way, depending on the installation:

• for an "old' cap, the above empty nuxeo-jsf-ui (with target platform cap) satisfies the dependency.
• for a server then the marketplace nuxeo-jsf-ui (with target platform server, built by the distribution) satisfies the dependency.