Augment the TransformManager so it can maintain the 4th column as
double precision; we accomplish this by storing an extra float3 per matrix.
It's calculated as `doubleTranslation - float3{doubleTranslation}`.
We also add methods to set and get a transform as mat4, internally only
the 4th column is kept as double precision.
Finally when we calculate the worldTransform, we take this extra data into
account, but only for calculating the new 4th column, so the extra work
is small.
math/mathwfd.h forward declares all {mat|vec}{2|3|4}<> classes,
which allows us to remove their respective #include in a lot of
our public headers.
Our math headers are full of templates, so this should help build times
a bit.
Also we want to keep the public headers as minimalist as possible.
