Merge branch 'release-1.2.11' into develop

* release-1.2.11:
  Bumping version to 1.2.11
  Update CHANGELOG entry
Add support for the "configure get" subcommand

This allows a user to print a single configuration value
from their AWS config file.  It only looks in the config file, does not
look in env vars, command line args, etc.  It supports scoped values (to
a specific profile) as well as explicitly specifying a section name via
(`section-name.config-value`).

In order to support this, I added support for positional arguments in
the Command class arg table.  I also added support for reading
descriptions/examples from a specific file, rather than relying on the
default value.  This is needed for subcommands, unless we pass through
parent command information to subcommands.
Add support for a "configure set" command

This allows a user to set a single configuration variable
without having to edit the contents of the config file.

This makes it possible to completely shield the user from knowing
where the config file is.

This supports the same syntax as "get" with respect to the qualified
and unqualified names.
Update CHANGELOG with get/set commands
Fix python3 bug regarding arg ordering

Need to ensure args match the same order as the ARG_TABLE
list.
Incorporate review feedback
Move changelog entry to next release
Merge branch 'config-get-set' into develop

* config-get-set:
  Move changelog entry to next release
  Incorporate review feedback
  Fix python3 bug regarding arg ordering
  Update CHANGELOG with get/set commands
  Add support for a "configure set" command
  Add support for the "configure get" subcommand
Remove filters section in doc gen

This is now added directly in the `--filters`
argument section.
Update test with latest snippet of latest EC2 model
s/executer/executor
Merge branch 'executor' into develop

* executor:
  s/executer/executor
Merge branch 'remove-filters' into develop

* remove-filters:
  Update test with latest snippet of latest EC2 model
  Remove filters section in doc gen
Use a single IO thread when downloading S3 objects

We have seen issues on some OSes that have trouble with
concurrent IO threads to different parts of the same file.
Despite these being non overlapping parts of the file, this
doesn't always work.

The fix is to switch to a single IO thread. All other threads are
now passed an IO queue in which they can submit either `IORequests`
or `IOCompleteRequests` that the IO thread understands.
Merge branch 'single-writer' into develop

* single-writer:
  Use a single IO thread when downloading S3 objects
Update changelog with next release version
Update package_data to pull in get/set doc examples
Bumping version to 1.2.12
Merge branch 'release-1.2.12'

* release-1.2.12:
  Bumping version to 1.2.12
  Update package_data to pull in get/set doc examples
  Update changelog with next release version
  Use a single IO thread when downloading S3 objects
  s/executer/executor
  Update test with latest snippet of latest EC2 model
  Remove filters section in doc gen
  Move changelog entry to next release
  Incorporate review feedback
  Fix python3 bug regarding arg ordering
  Update CHANGELOG with get/set commands
  Add support for a "configure set" command
  Add support for the "configure get" subcommand