Command jdbc:ds-factories is not documented

The command jdbc:ds-factories is not documented. This is important because the command exposes the driverName and driveClass needed by the jdbc:ds-create command.

The current documentation uses a Derby database which has an obvious driverName. The PostgreSQL driver name is not obvious and finding the name can be a source of frustration for new users.

1. Suggestions:
   Add documentation of jdbc:ds-factories
2. Reference jdbc:ds-factories as the source of driverName and driveClass to the descriptions of the jdbc:ds-create options -dn and -dc

Output of --help and the command

karaf@root()> jdbc:ds-factories --help
DESCRIPTION
     jdbc:ds-factories

    List the JDBC DataSourceFactories

SYNTAX
     jdbc:ds-factories

karaf@root()>

karaf@root()> jdbc:ds-factories
Name │ Class │ Version │ Registration bundle
───────────────────────┼────────────────────────────────────────┼───────────────────────┼───────────────────────────────
derby-native │ org.apache.derby.jdbc.AutoloadedDriver │ 10.14.2000000.1828579 │ derby [246]
derby │ org.apache.derby.jdbc.EmbeddedDriver │ │ org.ops4j.pax.jdbc.derby [247]
PostgreSQL JDBC Driver │ org.postgresql.Driver │ 42.2.8 │ org.postgresql.jdbc42 [159]
karaf@root()>

Example of creating a PostgreSQL Datasource named "testdsn for the database "test" on "localhost"

karaf@root()> jdbc:ds-create -dn "PostgreSQL JDBC Driver" -url "jdbc:postgresql://localhost:5432/test" --username testuser --password testpwd testdsn