Fix Gauge Converter

[jlevesy]

What does this PR do?

Couple of tiny fixes for the JSON to YAML converter regarding gauges.

• When the orientation from a gauge could not be determined, we tried to log a warning message, except that we logged the value from the StatPanel not the GaugePanel which is nil, causing a panic
• auto is a value that might be returned from grafana. So instead of logging a warning, this PR makes the converter handles the auto value instead explicitely.

Hope this helps :)

[codecov-commenter]

Codecov Report

Merging #230 (85b1305) into master (339a3c5) will not change coverage.
Report is 1 commits behind head on master.
The diff coverage is 50.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #230   +/-   ##
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  Coverage   40.99%   40.99%           
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  Files          39       39           
  Lines        2583     2583           
=======================================
  Hits         1059     1059           
  Misses       1484     1484           
  Partials       40       40           

Files Changed	Coverage Δ
internal/pkg/converter/gauge.go	55.00% <50.00%> (ø)