Text field auto size

Hi Daniel,

This adds auto-sizing capabilities to TextField. I broke the pull request into two commits - the first, "trim trailing whitespace", just removes trailing whitespace from the affected files (my editor does this automatically, and I didn't want the whitespace changes to be mixed in with the actual patch and make everything hard to read).

The commit notes should be self-explanatory, I hope.

This is intended to address the https://github.com/PrimaryFeather/Starling-Framework/issues/169 open issue