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/
Why do we divide by 100 here? This may need a comment and we should also add brackets because of the type coercion. `(times / 100) + "em"`