improvements in logging, examples and documentation

[skaarthik]

three commits each covering improvements in one area

[codecov-io]

Current coverage is 76.26%

Merging #294 into master will decrease coverage by -0.20% as of 05fd3cb

@@            master    #294   diff @@
======================================
  Files           40      40       
  Stmts         3930    3982    +52
  Branches       340     340       
  Methods                          
======================================
+ Hit           3005    3037    +32
  Partial        142     142       
- Missed         783     803    +20

Review entire Coverage Diff as of 05fd3cb

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[skaarthik]

This PR does not add any new code to the adapter or worker projects other than logging. Code coverage number dropped probably because some of the methods updated with logging are not already covered by unit tests. Normally code coverage failure in a PR means it is not ready for merge. Since only log entries are added to the classes covered by CC in this PR, I would like to treat this as an exception. Let me me know if you have any concerns.

[danielli90]

We may want to be consistent with either "examples" or "SparkCLR app". So the reader knows that, the examples can run in all three environments.

[skaarthik]

Well, the idea is that beginners might want to try out examples in local mode. When they are past that stage, they might want to tweak examples and run their apps in spark cluster. Agree that we need to make it clear that examples can be run anywhere. Will add a note on that.

[danielli90]

If we just say "Run SparkCLR app in local mode", with actual md talks about examples in local mode/standalone cluster/yarn cluster, the reader will just get it.

[danielli90]

Agreed with codecov exception.