Starter images; 'New' now brings up a selection dialog showing 'Starter'
images and color choices.)
New images can be given solid background colors (which the 'Eraser' tool
erases to).
Improved --usage output.
Added support for "--papersize help" to list papersizes available via libpaper.
Some Magic tools that apply an affect once per click-and-drag no longer
recalculate the effect on pixels that have already been affected (until mouse
button is released and clicked again).
Created Mirror and Flip Magic tools as plugins (except sound); hooks
added to Magic plugin API to allow starter and starter-undo mirror/flip.
Created Fade and Darken Magic tools as plugins.
Moved magic tool sounds to 'magic'.
Added flip and mirror icons to main Tux Paint UI (used to share magic tools')
Created 'tp-magic-config.sh' to get CFLAGS for compiling magic tool plugins.
Improved magic tool plugin API.
Committed some documentation on magic tool plugin API.
