Reorganize track documentation

[kytrinyx]

We have two types of track documentation:

• basic structural information
• common tasks/activities

This reorganizes the basic structural information:

language-tracks/
├── configuration
│   └── linting.md
├── documentation
│   └── for-consumers.md
└── exercises
    ├── README.md
    ├── anatomy
    │   ├── README.md
    │   ├── readmes.md
    │   └── test-suites.md
    └── versioning.md

This updates all the internal links. We will need to update external links to these pages after this gets merged.

[kytrinyx]

Notes to self:

maintaining-a-track/track-level-linting-with-configlet.md -> language-tracks/configuration/linting.md
maintaining-a-track/writing-documentation.md -> language-tracks/documentation/for-consumers.md
maintaining-a-track/managing-the-curriculum.md -> language-tracks/exercises/README.md
maintaining-a-track/anatomy-of-an-exercise.md -> language-tracks/exercises/anatomy/README.md
contributing-to-language-tracks/exercise-readmes.md -> language-tracks/exercises/anatomy/readmes.md
contributing-to-language-tracks/exercise-test-suites.md -> language-tracks/exercises/anatomy/test-suites.md
maintaining-a-track/exercise-versioning.md -> language-tracks/exercises/versioning.md

grep -l -r exercise-readmes.md .

• [x] ./clojurescript/README.md
• [x] ./coq/README.md
• [x] ./dart/README.md
• [x] ./fortran/README.md

[kytrinyx]

OK, fixed all the links I could find.