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]
Move Play detection into a utility module

The utility encapsulates the decision to search for Play applications
in the application root directory and its immediate children.

This utility is used by the Play container and will be used by the
Play auto-reconfiguration framework.

[#49696097]
Rename auto-reconfiguration framework

Since this framework is Spring-specific and we are about to introduce
a Play auto-reconfiguration framework, rename this to
SpringAutoReconfiguration at the risk of
floccinaucinihilipilification on the part of others.

[#49696097]
Create Play auto-reconfiguration framework

This uses the Play application directory detection utility to see
if there is a Play application configuration file present and if
there is, it contributes the auto-reconfiguration JAR (which includes
both Spring and Play auto-reconfiguration logic) to the library
directory for inclusion in the Play application's classpath.

[#49696097]
Mutate classpath in Play start script

Add any JARs provided by frameworks to the Play start classpath by
rewriting the start script.

[#49696097]
Share Play detection between container and framework

Move Play container detection into the shared utility class so that
it can be reused by the Play framework.

[#49696097]