Fix typos in doco.

Refs #3544.
It's confusing to name an ImageFunction that reads PNG images "tif".

Refs #3544.
file_range is a vector input, so we should format it as such.

In any case, saying `file_range = 00` is just confusing, because it
seems like you are providing a string when really you are just writing
the integer 0 in a weird way.

Refs #3544.
Fixing the issues with {dual,quad}_flip in VTK-6.

VTK-6 algorithms only seem to work with SetInputConnection() rather
than SetInput().  These fixes may also be backwards-compatible with
VTK-5, need to check.

Refs #3544.
Fixing/regolding the flip_quad test.

There were a lot of issues with this test, but it now works with VTK-6
and produces a 4-fold symmetric image, which was the original intention
of the test.

Refs #3544.
Unifying the VTK-5 and VTK-6 code paths in the ImageFunction class.

Refs #3544.
Merge pull request #4021 from jwpeterson/image_function_fixup

Image function fixup