Allow some ansible libraries to be imported on Windows

The intention is to allow ansible-inventory-grapher to run on
windows. Windows-specific issues with other parts of the codebase
definitely still exist

Remove unix specific dependencies from ansible.utils to ansible.utils.unix
Removed unwanted pwd import from ansible.constants
Import display_function in ansible.utils only when required
Fixed broken path construction for loading host and group vars
Handling filenames that windows doesn't like (typically globs
for hosts in inventory - e.g. web*)

There's a weird copyright conundrum as a result of this change, in terms
of attribution for the additional python module. git blame suggests that
@tbielawa contributed the functionality and so I've credited him in the
copyright for the file.

I did indeed contribute this code for the pause plugin. It is very very *nix specific.

Thanks for thinking of me!

Just a bit of nit-picking about the copyright header (feel free to ignore this, I won't be offended)

http://www.gnu.org/licenses/gpl-howto.html - "How to use GNU licenses for your own software"

"For software with several releases over multiple years, it's okay to use a range (“2008-2010”) instead of listing individual years (“2008, 2009, 2010”) if and only if every year in the range, inclusive, really is a “copyrightable” year that would be listed individually; and you make an explicit statement in your documentation about this usage.

Always use the English word “Copyright”; by international convention, this is used worldwide, even for material in other languages. The copyright symbol “©” can be included if you wish (and your character set supports it), but it's not necessary. There is no legal significance to using the three-character sequence “(C)”, although it does no harm."

See also: http://www.law.cornell.edu/uscode/text/17/401 "17 U.S. Code § 401 - Notice of copyright: Visually perceptible copies"