Switch roles of snake and echo

Snake is stateful so it should be one per connection. Echo is the
opposite.
Upgrade to Spring 4.0.0.M3
Update to 0.5.0.M2
Back to SNAPSHOT for dev
Add spring-messaging
Support javaagent instrumentation with loader

Update spring-boot-loader to allow `-javaagent` instrumentation when
running from executable jars.

Prior to this commit the `Launcher` skipped the application classloader
and instead used the system classloader as a parent. This was to ensure
that locally packaged classes were always loaded by the classloader
that had access to nested jars.  Unfortunately when using the
`-javaagent` option, it is the application classloader that is modified.

The `Launcher` class now uses the application classloader as parent
and `LaunchedURLClassLoader` has been updated to always search local
URLs before delegating to the parent. This is very similar to the way
that most application servers handle the loading of war files.

Issue: #56232870
Fix LaunchedURLClassLoader Java 1.6 compatibility
Refine LaunchedURLClassLoader load order

Refine the loading order of LaunchedURLClassLoader to consider the
root loader before locally bundled classes.

The prevents classes from locally bundled JARs from replacing system
classes.

Issue: #56232870
Remove gradle
Increase sample test timeout
Hacking