Add support for configuring AJP connectors

When Bitbucket Server 5.0 switched from distributing a standalone Tomcat distribution to using Spring Boot to start Tomcat, support for configuring AJP connectors was implicitly removed--only normal HTTP/1.1 connectors can be used.

To facilitate reverse proxying Bitbucket Server with minimal configuration, and an efficient binary protocol for forwarding request and response data, support for AJP connectors should be restored. Using AJP avoids the need to manually configure the correct "secure" settings for the connector, for example, when terminating SSL at a reverse proxy.