Add custom center-point selection to Kaleidoscope tool

Adding useless features to useless tools is what I do!  ;)  I joke, I
love this tool even though it has no practical application.  Changing
the center point allows for some neat variations with no additional
overhead, so I was happy to implement it.
Standardize "Content-Aware Resize" name in code

Form/function names were previously split across every previous name
used in the tool.  Now they have all been standardized to some variation
of "Content-Aware Resize" (save for the filename itself, but that is
less important to me).
Add custom center-point selection to Pinch/Whirl tool

Fun to drag the mouse around the preview window on this tool.  Reminds
me of old Windows screensavers...
Fix bad tooltip on command bar

"Left" should have been "right" when describing the "Save preset"
button's relation to the drop-down box!
Add custom center-point selection to Distort -> Poke tool