Make template editor work at http://localhost:4200

[beepsoft]

Changed the way KeycloakUserHandler calculates the auth endpoint when editor is run at http://localhost:4200. For now it takes the value from window.authBase set in version.js by gulpfile.js. There's surely a better way to do this.

For this to work keycloak-realm.CEDAR.development.2023-07-05.json also needs to be updated in cedar-docker-build:
{
"clientId" : "cedar-angular-app",
...
"redirectUris" : [ ..., "http://localhost:4200", "http://localhost:4200/"],
"webOrigins" : [ ..., "http://localhost:4200", "http://localhost:4200/"],
}

[egyedia]

We need to further discuss this PR before merging.
When developing locally, although we run the main frontend with gulp, and that serves it up on http 4200, we do not access it directly.
We do access it through nginx, using https://cedar.metadatacenter.orgx .
Please describe the use case which is covered by this modification.

[beepsoft]

This would allow developing the frontend independently of the location of the backend, which in my case is in a VM, but it could be in the cloud as well. From the fronted development point of view both of these are remote.