Remove label sets + add is_remote to spancontext

[lzchen]

Fixes #68
From OT removing labelsets.

As well OT add is_parent in span context.

[codecov-io]

Codecov Report

Merging #75 into master will decrease coverage by 0.09%.
The diff coverage is 97.77%.

@@            Coverage Diff             @@
##           master      #75      +/-   ##
==========================================
- Coverage   98.67%   98.57%   -0.10%     
==========================================
  Files          14       14              
  Lines         753      774      +21     
  Branches       97      102       +5     
==========================================
+ Hits          743      763      +20     
  Misses          8        8              
- Partials        2        3       +1     

Impacted Files	Coverage Δ
azure_monitor/src/azure_monitor/options.py	100.00% <ø> (ø)
azure_monitor/src/azure_monitor/storage.py	99.31% <94.73%> (-0.69%)	⬇️
...nitor/src/azure_monitor/export/metrics/__init__.py	100.00% <100.00%> (ø)
.../src/azure_monitor/sdk/auto_collection/__init__.py	100.00% <100.00%> (ø)
..._monitor/sdk/auto_collection/dependency_metrics.py	100.00% <100.00%> (ø)
...monitor/sdk/auto_collection/performance_metrics.py	100.00% <100.00%> (ø)
...ure_monitor/sdk/auto_collection/request_metrics.py	100.00% <100.00%> (ø)
azure_monitor/src/azure_monitor/version.py	100.00% <100.00%> (ø)

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[lzchen]

https://travis-ci.org/github/microsoft/opentelemetry-azure-monitor-python

[hectorhdzg]

LGTM