Remove some unused variables, less verbose animation logic

[jherico]

This adds a Random utility class that provides more functionality than the existing rnd() function used in the multithreaded example.

It does some minor cleanup on the animation logic.

• glm::vec3 rotation replaced by float rotationAxis; because the X and Z values are never read or written.
• glm::mat4 model removed as it's only used as an intermediate value to write to the push constant structure
• The push constant structure is absorbed by ObjectData because there's no reason for separate storage, they're always 1:1
• Logic to initialize ObjectData, update it per-frame and extract the mat4 are moved into the structure itself, reducing the verbosity and amount of indirection required to access all the variables
• Where possible convert values to radians at initialization time rather than each update
• In a couple places where the logic was something like x = a + rnd(b) I've updated it to be random.real(a, a+b) which provides the same range of values but feels easier to read
• Eliminated unused variables stateT, posX and posZ

[jherico]

I've reproduced the original logic here, but I'm confused. glm::rotate expects an angle here, in radiants, but we're passing the output of a sin function. Two lines below we pass in deltaT * M_TAU without wrapping it in a sin. I'm not sure what the intent is.