Renaming variables for codebase consistency

Ι've been working on a research machine learning-based tool (link: http://groups.inf.ed.ac.uk/naturalize/ ) tool that analyzes source code identifiers and makes suggestions for renaming them. The goal is to reduce unnecessary diversity in variable naming and improve code readability. This pull request is only a small sample of the suggestions made for libgdx.

No functional changes were made in any of the commits.