Add the ExternalAuthenticationValve valve, which, if an externally
authenticated principal is available, reads the REMOTE_USER_GROUP
information from the Coyote request and adds the groups ("roles" in
Tomcat terminology) to the principal.

It also saves a complete copy of the request attribute map in the
princpial.  The new class ExternalPrincipal is used to achieve this.

Part of: https://pagure.io/dogtagpki/issue/1359

Two Tomcat version-specific implementations of
SSLAuthenticatorWithFallback exist, with much duplicate code.
Extract an abstract base class 'AbstractPKIAuthenticator' and
implement just the unique bits in the concrete classes.

Part of: https://fedorahosted.org/pki/ticket/1359

The PKIListener has been modified to verify that all subsystems
are running and to show the command to enable the subsystem if it
was disabled due to errors.

https://fedorahosted.org/pki/ticket/1406

This patch adds some new unit files and targets for starting instances
with nuxwdog, as well as logic within the pki-server nuxwdog module to
switch to/from the old and new systemd unit files.

It also corrects some issues found in additional testing of the nuxwdog
change scripts.

To use nuxwdog to start the instance, a user needs to do the following:

1. Create an instance normally.
2. Run: pki-server instance-nuxwdog-enable <instance_name>
3. Start the instance using:
   systemctl start pki-tomcatd-nuxwdog@<instance_name>.service

To revert the instance, simply do the following:

1. Run: pki-server instance-nuxwdog-disable <instance_name>
2. Start the instance using:
   systemctl start pki-tomcatd@<instance_name>.service

The code has been modified to fix tomcatjss and python-sphinx
issues.

This is the first of several commits.  This adds a LifecycleListener
to call init() on the nuxwdog client before any connectors or webapps
start up, and call sendEndInit() once initialization completes.

Code is also added to prompt for and test required passwords on startup.
All that is required to use nuxwdog is to start the server using nuxwdog.
An environment variable will be set that will trigger creation of the
NuxwdogPasswordStore.  We expect tags for the required passwords to be in
cms.passwordList

The Dogtag code has been modified to support both Tomcat 7 and 8.
All files depending on a specific Tomcat version are now stored
in separate folders. The build scripts have been modified to use
the proper folder for the target platform. The tomcatjss
dependency has been updated as well.

The upgrade script will be added in a separate patch.

https://fedorahosted.org/pki/ticket/1264

The tomcat, cms, and cmscore packages have been moved from base/common
into separate folders in base/server so that they can be built separately.