* libgimpwidgets/images/gimp-color-hex-entry.png
* libgimpwidgets/images/gimp-color-scale.png
* libgimpwidgets/images/gimp-color-selection.png
* libgimpwidgets/images/gimp-file-entry.png: real screenshot for these
widgets.
* devel-docs/libgimpwidgets/visual_index.xml: added this file so we
have a "visual widget gallery" in our docs.
* devel-docs/libgimpwidgets/Makefile.am
* devel-docs/libgimpwidgets/libgimpwidgets-docs.sgml: added
visual_index.xml.
* devel-docs/libgimpwidgets/images/gimp-*.png: placeholders for real
widget screenshots.