Improve quality and consistency of variable names.

[jfpettit]

Some variables do similar things across algorithms but are named inconsistently. For example, many variable names differ between the polgrad and qpolgrad algorithm sets. Sometimes, this is because the variables are quite different, but other times they're doing similar or even identical things, but are still named differently.

Ideally, all variable names will be unified to the same style and will be improved, so that it is easy to tell what a variable is by looking at its name.

This won't be difficult to do, it is just time consuming and requires patience and attention to detail. As such, it is a great way for a newcomer to get familiar with the code while also contributing to the project. 😄