Reimplement all editing functions

[HeroesGrave]

With the big update from #11 and #18, nearly all the tools, image operations and effects have been removed.

I'm working on getting them reimplemented as soon as possible.

Tools:

• [x] Pencil
• [x] Brush
• [x] Eraser
• [x] Bucket
• [x] Colour Picker
• [x] Line
• [x] Rectangle
• [x] Ellipse

Image Operations:

• [x] Clear
• [x] Clear + Alpha
• [ ] Resize Image
• [ ] Resize Canvas
• [x] Flip Horizontal
• [x] Flip Vertical
• [x] Shift
• [ ] Rotate Right
• [ ] Rotate Left

Effects

• [x] Invert
• [x] Grid
• [x] White Noise
• [ ] Perlin Noise
• [x] Simplex Noise
• [x] Simple Blur
• [x] Simple Sharpen
• [ ] Simple Edge Detect
• [x] Channel Filter

(The operations which change the image dimensions are crossed off because they won't work well with the new drawing/layering system due to each layer having it's own history. I need to find another workaround)

[HeroesGrave]

Done! (Except for the bugged ones)