Update scala.vim

[SRGOM]

Default remains unchanged but added an option to not use scala recommended style.

[ches]

I'm not sure I see value in a custom variable when Vim users should already be familiar with many established ways to override these (well known, well documented) settings directly for any language—after/ftplugin files or autocmds, project-local vimrc, external formatting tools like Scalafmt…