The binary breaking bonanza

[DavidGregory084]

I'm going to use this PR to batch up some breakage for 0.4

• Most importantly - changes ScalacOptions to be private[davidgregory084] to avoid bincompat concerns with changing it in future. Interestingly if you change something to be private[somepackage] in your latest commit the MiMa warnings go away, even though your changes are still binary incompatible with the previous release.
• Changes ScalacOption from a container of tokens: List[String] to option: String and args: List[String]. Equality is determined only by option. I think this makes more sense for users when filtering options, since when filtering an option users probably don't really care which arguments have been provided for that option.
• Adds ScalacOptions.other. This fixes ScalacOption case class unreachable from build.sbt #65 by providing an escape hatch from the options DSL.

[armanbilge]

• Interestingly if you change something to be private[somepackage] in your latest commit the MiMa warnings go away, even though your changes are still binary incompatible with the previous release.

I'm going to lose sleep over this one 😱

[armanbilge]

I've opened a PR to at least reproduce the issue in MiMa.

• Removing method while making trait package-private is NOK lightbend-labs/mima#699

[DavidGregory084]

I think these changes have waited long enough - I'm going to retrigger CI and then merge this