* app/core/core-enums.[ch]: add GimpAlignReferenceType enum
* app/core/gimpimage-arrange.c: support using a channel as
reference for alignment.
* app/tools/gimpaligntool.[ch]: support aligning with a list item,
image, selection, active layer, active channel, or active path.
Now similar in form and function to Inkscape Align/Distribute
dialog.
* app/core/core-enums.[ch]: add GIMP_ARRANGE_FOO values
to GimpAlignmentType, and change CENTER to HCENTER,
MIDDLE to VCENTER.
* app/core/gimpimage-arrange.c: extensively rewritten
to handle arrangement of objects, and to do the
required sorting of lists by offset.
* app/tools/gimpaligntool.[ch]: added ability to arrange
groups of layers etc with constant spacing. Also try
to change things so that the tool aligns with the
object that users expect intuitively.
* app/core/gimpimage-arrange.[ch]: added, utility function for
aligning and arranging things in an image.
* app/core/gimpitem-align.[ch}: removed, no longer needed.
* app/core/gimpimage-item-list.[ch] (gimp_image_item_list_align):
removed this function, no longer used.
* app/core/Makefile.am: changes described above.
* app/core/gimpguide.c: remove bit of cruft left accidentally.
* app/tools/gimpalignoptions.[ch]: remove "alignment type"
option, not needed at this point.
* app/tools/gimpaligntool.[ch]: numerous changes, most
importantly ability to align guides, and use them for
alignment. More work coming on this tool.
* app/tools/gimpaligntool.[ch]: major change in ui, to make
this tool behave like alignment tools found in vector apps.
now you select items by clicking or drawing a rubber-band
rectangle, add items by holding down shift, and then press
a button to align all the selected items.
* app/tools/gimpaligntool.[ch]: improve layout of controls. Add
radio buttons allowing selection of reference layer without
using Ctrl modifier. Handle removal of target or reference
layers from image more correctly. More to come.
