Fix _spanSecondaryId for span logs & add fine-level logging

[oppegard]

The _spanSecondaryId field wasn't included on span logs, meaning that links to span logs in the UI weren't working in certain cases for spring boot apps. I only implemented this feature in WavefrontClient (not the deprecated DI and Proxy clients).

Also added FINE-level logging of Wavefront data inWavefrontClient when the following methods are invoked:

• sendDistribution
• sendEvent
• sendFormattedMetric
• sendLog
• sendMetric
• sendSpan
• sendSpanLogs