Fixing memory leak in SpanStore

Merge pull request #41 from michaelhyatt/update_1.19.0

* Update the agent to Java APM agent 1.19.0
* Fix for crash on DevKit steps not implementing AnnotatedObject #39 
* Turning the lambda into explicit anonymous class and surrounding with try/catch - opportunistic fix for #40

Merge branch 'master' of

https://github.com/michaelhyatt/elastic-apm-mule3-agent

# Conflicts:
#	apm-mule3-agent/pom.xml
#	apm-mule3.8-agent/pom.xml

Merge branch 'master' of https://github.com/michaelhyatt/elastic-apm-…

…mule3-agent

Merge pull request #26 from michaelhyatt/MDC_support

Support for log correlation

Merge pull request #25 from michaelhyatt/update_1.15.0

Updated to Elastic APM agent to v1.15.0
Updated to ByteBuddy 1.10.8
Updated README instructions
Downgraded 3.8 clients to support Mule EE 3.8.0 to support later Mule 3.8 versions

Added support for agent 1.8.0 and Mule 3.9.3

Merge branch 'master' of https://github.com/michaelhyatt/elastic-apm-…

…mule3-agent

Added instructions for Mule 3.8 support.

Updated version