VOL-4890 - Create a v2.11 release notes page

conf.py
-------
  o Fixed voltha-helm-charts/README, rendering/viewing is html -vs- rst.

index.rst
release_notes/index.rst
-----------------------
  o Move legacy release notes from the top level index into release_notes/index.rst.
  o Manually sort files for display, sphinx alpha-sorted v2.11 before v2.2.

overview/contributing.rst
logging/centralised_log_analysis.rst
------------------------------------
  o Update web redirected URLs so they stop being logged by "make linkcheck".

release_notes/voltha_2.11.rst
-----------------------------
  o Update version strings to the latest captured in master/VERSION.
  o Added convenience URLs for gerrit, github and helm charts.
  o Change table format from csv to list-table:
    - Improve readability and maintainability.
    - Avoid run-on sentences, embedded urls span 4+ lines.
    - Also corrected a few lint/syntax checking problems due to line length.

Change-Id: I0a93d27884712b512957ae04f7f2f4f9f2952ec1
8 files changed