Bug Fixes

• Fixed NPE due to uninitialised ServletPlugin.clientSpanExtensions. Thx @felixoldenburg
• Remove dependency on jaeger-core to avoid duplicate dependencies. See jaegertracing/jaeger-client-java#279
• Attempt to fix empty eum.js by always specifying class loader when using ServiceLoader.load

Improvements

• Don't log warning if ES index mapping is incompatible 7335d2a