make lint-chart reporting enhancements

chart_version_check.sh
----------------------
  o shellcheck v0.9.0 cleanups
  o Rewrite empty version stirngs so they are visible in command output.
  o Added get_version_by_git so sources not showing a delta can
    have their chart version displayed during a command run.
  o Fixed a few corner cases where version string not available
    due to flow through conditoinal logic.
  o Chart modified but version unchanged error:
    - Report dir/Chart.yaml VS dir to be clear about file to edit.
    - Also report Chart.yaml version string.

todo.md
-------
  o Capture details of an error reported for future enhancement.
  o Not clear from output why an error was reported:
    + Show your work, display intermediate charts so the dependency
      chain source will be clear.

Change-Id: I49cdee1828d32d67f2efb914300308176529671c
2 files changed