VOL-4890 - VOLTHA 2.11 release notes page

VOL-4840 - v2.11 documentation

howto/release/index.rst
-----------------------
  o Relocate list of legacy release note links from the left margin main
    index into release_notes/index.html to condense the index.

overview/release_process.rst
----------------------------
  o Misc cleanups & edits: change v2.10 -> v2.11.

release_notes/voltha_2.11.rst
-----------------------------
  o Add Mahir(s) v2.11 release notes wiki to the document.
  o Component name and version expanded into a table that includes links to gerrit and github (wip).
  o Removed agent packages section from v2.10.

Change-Id: I79b35f2bc6aca51567e78f92285904cac7696f4b
6 files changed