ESlint JSdoc

[toasted-nutbread]

This change updates some JSDoc comments and adds linter rules to ensure they are configured correctly.

Currently, JSDoc comments aren't required for everything, since mandating them for all private functions is overkill. However, this can be changed in the future by adding this to .eslintrc.json:

        {
            "files": [
                "ext/js/**/*.js"
            ],
            "excludedFiles": [
                "ext/lib/**/*.js"
            ],
            "rules": {
                "jsdoc/require-jsdoc": [
                    "error",
                    {
                        "contexts": [
                            {"context": "ClassDeclaration"},
                            {"context": "FunctionDeclaration"},
                            {"context": "MethodDefinition[key.name=/^[^_][\\w\\W]*/]"}
                        ]
                    }
                ]
            }
        }