More Documentation Review Updates

[lihaoyi]

• Broke out a new top-level section The Mill CLI for what was previously Installation & IDE Support
  • Broke out Mill Command-Line Flags and Other installation methods into their own sections
  • Moved documentation for --interactive/--watch/--jobs into Mill Command-Line Flags
• Moved the Realistic {language} Example Project from build-examples to {language}lib/intro.adoc
  • This helps make a clearer separation between the "tutorial read-from-top-to-bottom" intro.adoc and the rest of the stuff in each language-specific section which is more "look up stuff as necessary"
  • Deleted the nested-modules example. Probably not important enough to deserve a full example/doc on its own
  • build-examples.adoc now only contains Example builds for real projects and Real World Mill Builds
• Add a reference to mill-mima under the Linting pages for Java and Scala (not sure if it works well with Kotlin so left that out)
• Add the missing kotlin web examples to the kotlin doc pages