0.8 - Turtle follows mouse

[ldpercy]

• Getting svg coordinates from a transformed document works
• Added a simple point info dropper for the clicked page location; it has cartesian and polar parts that switch off with their respective grids; there is also a clear button for it
• Still manually flipping some y-coords for SVG though - still needs a proper treatment
• A aside into trying to figure out a more consistent syntax for certain commands categories
• An even bigger diversion into trying to work some of the more abstract maths behind turtle movement - some useful ideas, but still in progress
• For now I'm distinguishing between points (x,y or r,a) and positions that also incorporate a direction or orientation
• For now I'm dropping 'heading' terminology in favour of 'direction' to make things super clear, might bring heading back later though
• New 'Position' class in PlanarSpace, starting to move some core Turtle maths to it; more as i figure it out properly
• Added a couple of new commands for moving to absolute x,y coords with/without drawing; all the syntax for this is still a bit up in the air
• There was/is a bit of weirdness around click events when i had both single and double clicks registered - in some cases the dbl didn't fire, and I haven't found out what's causing it yet. For now sticking with single clicks for everything.
• Have four options for page clicks - nothing, point info, move and draw. This will need to reviewed in the future though.
• Adjust colours a bit.