Inject existing groups at InventoryDir initialization

Bring groups handling in ini.py up-to-date (trivial fix)

Releases are named after Led Zeppelin songs as of 2.0.0.

Since c8f2483d, ini.py expects to always be passed in a pre-created list
of groups, and can no longer deal sensibly with an empty list; this just
makes that expectation clear.

Fixes #12563

Fixes #12560

Fixes #12536

Describe the units for fact_caching_timeout

This fixes a corner case where ini files live in a subdir
of the main inventory directory.

Reproducing the original error:

mkdir -p inventory/ini
cat > inventory/ini/hosts << EOF
[www]
www1
EOF

$ ansible -i inventory/ all -m ping
ERROR! 'all'

(or without the [www] group, it would complain about 'ungrouped')

Fixes #12505

Python 3: there's no basestring

Fixes another failing test.

(I don't want to do a global search/replace for 'basestring' because I
want to have unit tests covering each occurrence.  When I run out of
existing failing tests, I'll try to write new ones.)

* Remove extraneous imports
* Fix some error handling
* Enable pipelining
* Disable su since it doesn't work
* Add error message when installed docker is not recent enough to
  support this plugin
* Move nested functions to class level
* Make transport a class attribute
* Make exec_command, put_file and fetch_file more robust

Fixes #12524

* Disable su as it's not currently working 100% (and was disabled in v1).
* Move BUFSIZE out of the class to match other conenction plugins
* _connect shouldn't return self.

requested via play context

cloudstack: improvements and tests

#9130 rebase: EC2 Inventory Boto Profile Support

Re-order the methods in ssh.py so that methods needed for implementation are near and just above the relevant public methods.

Standard with the rest of the code base.

A couple of ssh cleanups

Make use of better error handling mechanism

Fixes merge conflicts and standardizes option naming

the use of boto profiles for separating credentials as
specified in

http://boto.readthedocs.org/en/latest/boto_config_tut.html