create-scala cleanup

- Cleanup comments
- Remove extraneous whitespace
- Remove commented code
ftdetect: remove unnecessary whitespace
ftplugin: add automatic comment formatting

Set 'formatoptions' to break comment lines but not other lines, and
insert the comment leader when hitting <CR> or using "o".
syntax: add XXX, FIXME, and NOTE highlighting.

Also removes support for TODO with different case; it makes the syntax
simpler, we often don't want all lowercase to be captured, and it should
probably be all caps anyway.
Update README