[docs] add design doc for location awareness
[docs] add design doc for location awareness

Added the design document for the location awareness feature.  I used
the pandoc tool (https://pandoc.org/) to convert it from the .html
format after exporting it from the original google docs format.
I manually removed comments and extra anchors.

At the time of writing, the original was available at:

  https://s.apache.org/location-awareness-design

Change-Id: Ibe913f19520024c43fbb8184cb8dd1f1e679ddec
Reviewed-on: http://gerrit.cloudera.org:8080/13000
Reviewed-by: Grant Henke <4cf7ebbe638391c4d27a10cf751b99bdbd1a1880@apache.org>
Tested-by: Alexey Serbin <864f6b82bd94e8dda64141d4274519ee66e0102e@cloudera.com>

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