Changes since previous release

HDView now supports multiple image editing tools including: paintbrush, clone stamp, eraser, eyedropper
- each tool can take over the top panel to provide options
  - e.g. paintbrush supports selecting radius, hardness, flow, angle, roundness, spacing and smoothness
- GUI shows selected tool's overlay on the image (e.g. the circle/ellipse of the brush)
- paint brush supports smoothing of mouse cursor movements using Chaikin's quadratic b-spline corner-cutting algorithm (centripetal Catmull-Rom also an option, but commented out)
Added a foreground/background color selection widget in the toolbar that is shared by all tools
keyboard shortcut code has been refactored so each tool handles it's own shortcuts
Info is now it's own panel on the left side
minor GUI fixes.

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