DDF-880 Review/refactor all error logging.

Probably the main thing to watch out for here is any inadvertent double-logging. There shouldn't be any functional issues.
I'm not the biggest fan of XLogger these days, but since it's already being used you can also do:
```java
logger.throwing(illegalArgumentException)
```
for many of these logs where you're just logging the exception and are putting in generic messages to fulfill the method. Might want to look at how it formats the log though to see if it's any better/more readable. 

Reference: 
http://www.slf4j.org/api/org/slf4j/ext/XLogger.html#throwing(T)
http://www.slf4j.org/api/org/slf4j/ext/XLogger.html#throwing(org.slf4j.ext.XLogger.Level, T)