Feast core crashes without logger set

[tims]

Expected Behavior

Feast core should start cleanly with a default logger if none is set.

Current Behavior

Feast core crashes without a logger set

Steps to reproduce

If I comment out logType: JSON in the helm chart feast core does not start
The pod enters a crash loop with:

2019-03-06 05:53:31,246 main ERROR JsonLayout contains an invalid element or attribute "objectMessageAsJsonObject"
2019-03-06 05:53:31,755 main ERROR Unable to locate appender "Appender" for logger config "root"
2019-03-06 05:53:33,143 main ERROR JsonLayout contains an invalid element or attribute "objectMessageAsJsonObject"
2019-03-06 05:53:33,147 main ERROR Unable to locate appender "Appender" for logger config "root"

[tims]

See this change PR #120