Overhaul introductory section of docsite

[lihaoyi]

Flesh out the intro to include answers to all the frequently asked questions, as determined by the recent discussion on reddit r/java and r/programming

Generally tried to make it more information dense and structured, covering the main points and elaborations in bullets, and with more detailed sections comparing against Maven, Gradle, and SBT. I tried to limit the descriptions to things that would be of most direct interest to Gradle/Maven users with zero knowledge of Mill or Scala, which means more empirical stuff (e.g. performance, IDE support, ease of customization) v.s. philosophical stuff (e.g. intuitive abstractions, pure FP, etc.)

I renamed all the Scala_ and Java_ pages to follow a consistent naming convention, and added forwarder aliases as necessary

[lihaoyi]

@lefou @lolgab do you guys use Gradle? I'm trying to come up with a third bullet point to put here, but not sure what it should be. What are the things a gradle user would find most interesting about Mill?

[lefou]

I don't. Beside the missing mental model in Gradle, since the build configuration isn't a one to one mapping to some internal structure, but rather some distant incoherent interpreter.

What else I suffered in Gradle when I tried it many many years ago (before 2010, don't know if that changed since), is the magical use of files in the directory tree (upwards and downwards). That's one of the reasons I often argue for explicit includes and the single source of truth concept in Mill.

[lefou]

I don't. Beside the missing mental model in Gradle, since the build configuration isn't a one to one mapping to some internal structure, but rather some distant incoherent interpreter.

What else I suffered in Gradle when I tried it many many years ago (before 2010, don't know if that changed since), is the magical use of files in the directory tree (upwards and downwards). That's one of the reasons I often argue for explicit includes and the single source of truth concept in Mill.