HTTPS configuration for Pax Web (#448).

New config properties in global POM:

    `org.osgi.service.http.port.secure` -- The HTTPS port. Default is 8443.

    `org.osgi.service.http.secure.enabled` -- To enable HTTPS set this to `true`. Default is false.

    `org.ops4j.pax.web.ssl.keystore -- The path to the .keystore file.

    `org.ops4j.pax.web.ssl.password` -- The **Key Password** (as entered in the `keytool`).

    `org.ops4j.pax.web.ssl.keypassword` -- The **Keystore Password** (as entered in the `keytool`).

Note the confusing wording of the 2 Pax Web password properties.

For `keytool` usage to create a keystore and a key pair and a self-signed certificate see #295.

See #448.