Canvas notes icons

More work on improving the icons for the body charts feature we are working on. These are in order:

- Move tool
- Pen tool
- Eraser tool
- Text tool
- Colour picker
- Undo
- Reset canvas to window size
- Zoom in
- Zoom out
- Back/cancel
- Save
- Pen/eraser tool sizes

Maybe the zoom in and out seem a bit vague here, but in context they are okay. I may add a magnifying glass yet I guess.

We are implementing these as inline SVG, which means we can change the colour of the eyedropper icon according to the chosen colour by styling the path of the SVG itself (see this if interested: https://css-tricks.com/using-svg/).