Add support for specific endpoint environment variables #188
  Add this suggestion to a batch that can be applied as a single commit.
  This suggestion is invalid because no changes were made to the code.
  Suggestions cannot be applied while the pull request is closed.
  Suggestions cannot be applied while viewing a subset of changes.
  Only one suggestion per line can be applied in a batch.
  Add this suggestion to a batch that can be applied as a single commit.
  Applying suggestions on deleted lines is not supported.
  You must change the existing code in this line in order to create a valid suggestion.
  Outdated suggestions cannot be applied.
  This suggestion has been applied or marked resolved.
  Suggestions cannot be applied from pending reviews.
  Suggestions cannot be applied on multi-line comments.
  Suggestions cannot be applied while the pull request is queued to merge.
  Suggestion cannot be applied right now. Please check back later.
  
    
  
    
Partially fixes #165
Refactored
OpenTelemetryEnvironment.Configureto account for specific endpoint environment variables. IntroducedOpenTelemetryEnvironmentVariableshelper, where all well-known OTEL environment variables are defined.More work needs to be done to support
OTEL_EXPORTER_OTLP_LOGS_PROTOCOL/OTEL_EXPORTER_OTLP_TRACES_PROTOCOLandOTEL_EXPORTER_OTLP_LOGS_HEADERS/OTEL_EXPORTER_OTLP_TRACES_HEADERSvariables, since with the current implementationIExporterdoesn't support different protocols for traces and logs.