Generic function wrapper stage

Add a Stage that wraps a given function of the form `OutputType(InputType)`. This would reduce the boilerplate code required to write simple stages with one input and one output (generically named "input" and "output").:
```
// processing function
GLuint limitMSAA(GLuint numMultisamples);

// Stage declaration
using LimitMSAAStage = FunctionStage;

// Alternative declaration of a creator function with Input/Output type deduction
static const auto limitMSAAStage = stageCreator(limitMSAA);
```

Could be extended/overloaded for functions with 2, 3, 4 inputs.

(Already have some code for this)