We now simply use `require()` to load plugins and Markdown highlighters.
Note that `@jsdoc/util.path.commonPrefix`, unlike `jsdoc/path.commonPrefix`, does not append `path.sep` to the return value.
Includes other minor cleanup.
- new Rhino .jar to help find module paths
(https://github.com/hegemonic/rhino/commit/31b70105)
- make __dirname and process.cwd() provide the current module path; use
only env.dirname for JSDoc's home dir; fix callers
- get rid of jsdoc/util/include (and update test framework accordingly)
- avoid running Rhino/Node.js tests on the wrong runtime
- remove support for global 'publish' function, which relied upon
jsdoc/util/include
- update jsdoc/util/dumper for consistency with Node.js'
JSON.stringify()
- fix jsdoc/util/runtime to detect Node.js correctly
- add Node.js versions of jsdoc/fs and jsdoc/path
- other minor cleanup
