GitLab

- Camera can now be freely positioned and target arbitrary spots
- New Camera is now a templated class in common/datatypes.hxx
- Vector source file has been moved to common/Vec.hxx
- The HIP and CUDA workarounds in Vector have been merged in the new
class
- SYCL is not yet converted and disabled because it's broken on my
machine, as is ROCM's OpenCL, which is quite annoying

Different implementations can have different ideas of what some things
mean. Though I haven't gone ALL the way they should be more consistent
now, particularly within Vulkan where they'd differ both on Vulkan
driver as well as SPIR-V source (GLSL vs HLSL vs OpenCL)

Also added one more tweakable parameter as well that scales value
throughout entire image

Vulkan still missing
SYCL maybe broken?

Didn't touch any of the CMake side though

- Window titles now specify flavour
- Program output times setup
- CPU based code was optimised (mainly by avoiding copies. ~10% faster)
- Both CPU and GPU code moved to float from doubles to help performance
from user-focuse GPUs (such as my own Titan X which was unable to beat
my CPU)