Save Script Editor preferences

This updates the Fiji Script Editor to save and restore preferences for a few things, including tab size, font size, line wrap, emulated tabs and window size. It is largely the work of @sinverso, rebased to fix some whitespace issues.

I also restored the language-specific tab size behavior, in particular for Python which resets to tab size 4 every time that Python is selected as the language, or a Python script is opened. While this behavior may not be completely ideal (I agree with @dscho that ideally, the tab size would simply be persisted per-language), the current approach will suffice for now, in the interest of getting these improvements merged quickly.