OPENDJ-2017 (CR-7035) Setup GUI: Fix replication setup

* src/main/java/org/opends/admin/ads/ReplicaDescriptor.java
** Add the backend object classes as field to retrieve type of backend (JE, persistit...)

* src/main/java/org/opends/admin/ads/ServerDescriptor.java
** Add logic to add backend object classes to the replica descriptor

* src/main/java/org/opends/quicksetup/installer/Installer.java
** Fix a regression introduced in r10231
** Do nothing if the server is the first in replication topology instead of seting baseDNs of userRoot backend
** Remove the userRoot backend deletion (as it is not hardcoded in the config.ldif since r12022)
** Retrieve backend type from backend object classes to allow creation of different kind of backend

* src/main/java/org/opends/quicksetup/installer/InstallerHelper.java
** Replace createLocalDBBackend(...) by createBackend(...) and change the code to be generic to allow both creation of JE and pluggable backends

* src/main/java/org/opends/quicksetup/util/Utils.java
** Removes the dsconfig create-replication-domain added in equivalent command line. This comment is not needed and avoid replication of suffix content.

* src/main/java/org/opends/server/tools/BackendTypeHelper.java
** Add methods to adapt a backend type from a config object or a backend name