Add file chooser facade and support for Linux and Windows

[depau]

I renamed the branch to avoid confusion with qua-non's branch (native_dialogs) and reopened this pull request. It should be up to date with master now.

Needs testing for Windows.

The Mac OS X implementation will be ported soon.

[depau]

I added support for Mac OS X,. but it needs testing.
Particularly, I need you to test:

• multiple=True - multiple file selection, please report any exceptions
• filters=[list of wildcards] - provide a list of wildcards like this: ["_.mp3", "_jpg", "JPG", "pn"]
• filters=[list of extensions], use_extensions=True - provide a list of extensions like this: ["mp3", "jpg", "png"]

[tito]

That's awesome!

[akshayaurora]

@Davideddu could you rebase? there is a conflict while merging right now.

[depau]

@akshayaurora Done.

[depau]

Please make sure you edit the README to add the line for the IR blaster. Also I had to add "irblaster" to all in plyer/init.py