Play version

Previously, the detect output of the Play container was simply 'play'
without a version of the Play Framework being used.  As the detect
output is intended to be used to determine when applications a
susceptible to security exploits, it was important to output that
version.  This change attempts to determine the version by looking at
the Play JAR and extracting it's version number from it.

[#52855559]
Merge 52855559-play-version to master

[Completes #52855559]
Ignore non-core play jars

Previously, the Play detection algorithm would detect non-core play
JARs.  This change ensures that only JARs matching
/.*play_[\d\-\.]*\.jar/ will trigger detection.

[#52855559]
Merge 52855559-other-play-jars to master

[Completes #52855559]
Add RemoteIpValve

As the Tomcat instance created by this buildpack is always located
behind a proxy, this change adds the RemoteIpValve to the Tomcat
configuration.  This change ensures that functionality such as
HttpServletRequest.isSecure() works properly in the Cloud Foundry
environment.

[#52956737]
Merge 52956737-remote-ip-valve to master

[Completes #52956737]
PostgreSQL repository builder

This change adds the PostgreSQL repository builder to the documented
list of repository builders.

[#53156523]
Merge 53156523-new-repository to master

[Completes #53156523]
Merge commit 'cae0c41f03ed43b446fab8f0b8fdf349f6c23617'