Streamline log() and outputToLog()

[drance]

The ObjC AspenHelpers currently log without the handy emoji prefixes. This is because that formatting is done in the private outputToLog() function, which ObjC can't call. Rather than make outputToLog() public so ObjC can see it, suggest (review with @justin):

• remove outputToLog(), and rewrite verbose(), info(), etc. to call LogFormatter directly. This saves a method call and autoclosure capture / alloc per log statement, and isolates the implicit nature of the formatter to the convenience methods
• remove the unused logger param from LogFormatter.formatLog()