Improve Tomcat logging format and location

Previously, the Tomcat logs (and that of anything else that used JULI)
were written in an unreadable form to stderr.  This made the logs
difficult to use when diagnosing problems, but also very scary looking
when the started with [ERR].  This change updates the buildpack to use
a new copy of the Tomcat support JARs which, when combined with new
logging configuration, will cause the output to be cleaner and be
written to stdout.

[#64764934]
Merge 64764934-tomcat-logs to master

[Completes #64764934]
Additional JARs on classpath

As part of the work to integrate Ratpack into the buildpack, an
adjustment to the Groovy classpath has been made.  Previously, Groovy
applications were responsible for maintaining their own classpath.
Instead, the buildpack should be doing this.  The new behavior is that
all JAR files (regardless of their location) will be added to the
Groovy classpath at runtime.

[#63888002]
Merge 63888002-ratpack-sample-application to master

[Completes #63888002]
Ratpack support

This change adds support for running Ratpack[1] applications.  The
Ratpack support is added as a container and will trigger on the
existence of a app/{R,r}atpack.groovy configuration file.

[1]: http://www.ratpack.io
Merge 63798400-ratpack to master

[Completes #63798400]
Handle invalid encodings

Previously, there was a bug where files that were encoded as something
other than UTF-8 could cause the buildpack to fail.  This change
handles those cases.
Merge branch 'master' of github.com:cloudfoundry/java-buildpack