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.
API changes:
+ No more `jsdoc/template` module. Each JSDoc template uses whatever templating system it wants.
+ No more TaffyDB. Each template finds doclets however it wants. (TODO: Update `jsdoc/util/templateHelper` so none of its methods expect a TaffyDB object.)
+ Templates are now loaded with `require('my-template-name-here')`. The resulting object must include a `publish` method.
+ The `publish` method now takes two parameters: a `data` object with `doclets` and `tutorials` properties, and an `options` object. `data.doclets` is just an array.
Other notable changes:
+ No more `haruki` template.
+ Moved the `default` and `silent` templates to new packages.
+ The `.tmpl` files for the `default` template (now called `@jsdoc/template-original`) no longer use custom delimiters.
