Temporarily disable all but the classic Mandelbrot on this branch.
Move MINIMUM_PIXEL_SIZE into a traits class.
ChunkDivider should cast to Value, not to double.
Fractal should use logl for now, not log.
Rewrite Mandelbrot as template-driven
Create value_e identifying the type of value arithmetic to use.
Plot3Plot passes it on (currently fixed) to ChunkDivider, then to Plot3Chunk, then to the fractal impl.
Placeholder trait impl for long double.
Pick the most appropriate maths for the plot, given the pixel size limits.
Create Fractal::smallest_min_pixel_size() for use by UIs.
Add lookup table for value type names
Enable value_traits<long double>
MainWindow::do_plot now catches exceptions
Use fabsl instead of fabs
Another vgsupps tweak for raring
We don't need AXIS_LENGTH_PRECISION any more.
Create MathsMixin helper and template-tastic Mandelbrot definition
Bring Mandelbrot_Generic back online
Refactor the remaining Mandelbrots into the new form
Refactor and re-enable Mandelbar
And refactor and re-enable Mandeldrop and Misc.