Add key_file and accept_hostkey to ansible-pull

[Vagrant guide] Updating private key location

Since Vagrant 1.7.0, released in December 2014, the private key file is autogenerated and has a new location - check the changelog for more info: [version 1.7.0 changelog](https://github.com/mitchellh/vagrant/blob/master/CHANGELOG.md#170-december-9-2014)

Fix documentation on hostfile vs inventory , follow up of #10130

Signed-off-by: Max Riveiro <kavu13@gmail.com>

http://michaeldehaan.net/post/109595670406/happy-trails-ansible

also added commented out entries in ansible.cfg to show other options

Configure retry file usage and location

Add shell script to fast update ansible repo

Fix for memory fact gathering

Saner ansible-pull output

https://github.com/ansible/ansible/pull/10129#issuecomment-72077500

* Switch default value from 0 to None.
* Prefill keys with default value so that determining calculated values
  is easier

made inventory consistent in config file, deprecated old config hostfile

Report location (filename and line number) for inventory syntax errors

Expose more facts about user on host system

I have a host which started to fail while gathering facts after the addition
of expanded memory facts in PR #9839:

Traceback (most recent call last):
  File "/home/ansible/.ansible/tmp/ansible-tmp-1422536976.05-133253824703289/setup", line 4278, in <module>
    main()
  File "/home/ansible/.ansible/tmp/ansible-tmp-1422536976.05-133253824703289/setup", line 137, in main
    data = run_setup(module)
  File "/home/ansible/.ansible/tmp/ansible-tmp-1422536976.05-133253824703289/setup", line 81, in run_setup
    facts = ansible_facts(module)
  File "/home/ansible/.ansible/tmp/ansible-tmp-1422536976.05-133253824703289/setup", line 4217, in ansible_facts
    facts.update(Hardware().populate())
  File "/home/ansible/.ansible/tmp/ansible-tmp-1422536976.05-133253824703289/setup", line 2339, in populate
    self.get_memory_facts()
  File "/home/ansible/.ansible/tmp/ansible-tmp-1422536976.05-133253824703289/setup", line 2375, in get_memory_facts
    'cached': memstats['swapcached']
KeyError: 'swapcached'

My problem host doesn't have SwapCached in /proc/meminfo. It may be better to
set defaults for these keys, since the values provided by /proc/meminfo can
change from version to version.

Fixes #10110