Fix #28816: Error when importing obj file with texture due to api change

Update obj importer and xcf importer to use new post-texface api.

* You only have to do layout.prop if you want 1 property, no need for row then!
* Use col, row, sub as variable names, not colsub, rowsub, row2 etc please.
* Povray Addon: Still used a lot of splits, you need no split when you only have 1 column! 

alpha layer if this layer is unmodified (pure white) even if the layer
is marked as alpha. This makes it impossible to know without phisically
checking if the alpha file exists or not

READ THIS TO AVOID A LOT OF WORK!

New way of linking to tracker pages: just use the parameter "aid" (artifact ID),
to avoid a lot of manual updates later in wiki and svn.

Example:
=========

OLD WAY TO LINK TO TRACKER
-----------------------------

Complete url of a script in Upload
http://projects.blender.org/tracker/index.php?func=detail&aid=25349&group_id=153&atid=467

If we move this in contrib this url will become
http://projects.blender.org/tracker/index.php?func=detail&aid=25349&group_id=153&atid=468
467 becomes 468, so we have to update this in wiki page.

Later on, when this moves into Trunk, the url will become
http://projects.blender.org/tracker/index.php?func=detail&aid=25349&group_id=153&atid=469
468 becomes 469, so we have to update the url in wiki page and svn.

Annoying!

NEW WAY TO LINK TO TRACKER
-----------------------------

Best way to link to tracker page is using:
http://projects.blender.org/tracker/index.php?func=detail&aid=25349

Use "func=detail"
Use "aid"            (which is the "artifact ID")

DON'T use "group_id" (which is the project ID, bf-extensions is project 153)
DON'T use "atid"     (which is the "artifacts tracker ID")

Like this, the url is unique, and we will avoid to update wiki pages and svn after moving pages
 


[[Split portion of a mixed commit.]]

- in wiki page urls: "File_I-O/"     -> "Import-Export/"
- in categories:     "Import/Export" -> "Import-Export"
- 1 tab to 4 spaces
- some tuple formatting, just to be very picky :P

discussion over naming conventions

http://wiki.blender.org/index.php/Extensions:2.5/Py/Scripts/File_I-O/GIMPImageToScene