GPII-1014: Replace the slider adjuster for cursor size with plus/minus text field adjuster

The bug report: http://issues.gpii.net/browse/GPII-1014

This pull request also upgraded the infusion library to be in sync with the latest master: https://github.com/fluid-project/infusion/
After more discussion with Dana and Justin today, it's decided to use "increase" and "decrease" with more specific info like "increase/decrease text size".