Restructure project to follow standard Maven Standard Directory Layout

[aSemy]

Currently Knit does not follow the Standard Directory Layout

kotlinx-knit/build.gradle.kts

Lines 49 to 53 in c4e77da

	sourceSets {
	main.kotlin.dir = "src"
	test.kotlin.dir = "test"
	main.resources.dir = "resources"
	}

While this reduces the number of directories that the project has, I find it makes it much more difficult to navigate as the new files don't follow the conventions that most projects use, and it's unclear what files are within which subproject.

[qwwdfsad]

We are moving towards complete the opposite: https://youtrack.jetbrains.com/issue/KTIJ-20411/Project-wizard-should-provide-an-option-to-create-compact-directory-layout-common-package-prefix and https://youtrack.jetbrains.com/issue/KTIJ-23274/First-party-support-of-compact-directory-layout-common-package-prefix, so closing as "won't fix".

Tickets have pretty self-describing rationale I do hope

[aSemy]

Oh okay, that's a bit weird and confusing. IntelliJ automatically collapses them so it's not a big difference. But okay.

Anyway, implementing buildSrc convention plugins means there's no need for nested subprojects, which would probably help just as much, and make it clear about what files belong to which project.

I'll see if I can update the PR #51 to something like this?

.
└── kotlinx-knit/
    ├── kotlinx-knit-core/
    │   ├── src/
    │   │   ├── Knit.kt
    │   │   └── ...
    │   ├── test/
    │   │   └── ...
    │   ├── testResources/
    │   │   └── testdata/
    │   │       └── ...
    │   └── build.gradle.kts
    └── kotlinx-knit-gradle/
        ├── src/
        │   └── KnitPlugin.kt
        ├── resources/
        │   └── knit.properties
        ├── test/
        ├── testResources/
        ├── testFixtures/
        ├── testFixturesResources/
        └── build.gradle.kts