Logging custom annotations for PHOENIX-1198

[elilevine]

This PR adds custom annotations to log lines generated in Phoenix's client-side code. It builds on PR #13 and uses the same mechanism to pass custom annotations to connections. These custom annotations are only added to client-side code logging that is within the context of a user operation (meaning a PhoenixConnection is available). No new log lines are added here. Only existing log lines are changed.

Usage:

1. Add custom annotation properties when creating a Phoenix Connection. e.g. phoenix.trace.custom.annotation.a1=v1
2. Log lines in (some of) Phoenix's client-side code would look like this: {a1=v1} something logged

Ignore the following files here, since they are covered in PR #13: BaseTracingTestIT.java, PhoenixTracingEndToEndIT.java, TraceReader.java, Tracing.java, JDBCUtilTest.java

@jtaylor-sfdc

[JamesRTaylor]

How about adding a custom annotation for known properties like TENANT_ID and CURRENT_SCN?

[elilevine]

Good call. Will add.

[jyates]

This would be a lot nicer if you didn't mix the logging changes with the tracing changes - the changelist would be much more succinct and to the point. Otherwise, seems like the right approach, though it could use some cleanup (docs, readability, etc)

[JamesRTaylor]

Had an offline conversation with Jesse and he had a good idea. Can we change the property name by dropping the "trace" part of it and have this instead? I don't think having "custom" in there adds anything either. How about just phoenix.annotation? Then you can use these for tracing and logging both.

[elilevine]

I like it. Good call.

[elilevine]

Merged now.