enable optional JSON logging to console

[labkey-willm]

This adds two new optional env vars:

• LOG4J_CONFIG_FILE: uses the included local log4j2.xml by default, but can be set to alternates (if they exist wlin the image, like server/labkeywebapp/WEB-INF/classes/log4j2.xml for the default embedded file)
• JSON_OUTPUT: false by default to maintain existing functionality, but can be set to true to output all java logs as JSON; tomcat and access logs are still non-JSON for now

This also updates the default log4j2.xml to more closely match the current default 'server' version.

[labkey-jeckels]

I take it that you want the non-JSON HTTP access logs for now?

[labkey-willm]

I take it that you want the non-JSON HTTP access logs for now?

Yeah, it's fine for now. I'll circle back to make matching changes to Dockerfile's application.properties once the json access log bits are available in the server.