…uredTags` setting to control whether the type and namepath portions should be checked for validity and whether such portions are required, and to let user-defined "namepath-defining" tags be added to defined types. Closes gajus#481

BREAKING CHANGE:

Drops `checkSeesForNamepaths` setting. Use `{settings: {jsdoc: {structuredTags: {name: 'namepath', type: false, required: ['name'],}}}}` instead.

Also:
1. Clarifies in more cases where a problem is specific to the mode or not
2. Reports simultaneous invalid name *and* type errors
3. `typdef` now requires `allowEmptyNamepaths: false,` to report empty names (as with other tags)
4. Requires a name for `event` and `external` (and `extends` in jsdoc mode); some tweaking of other tags per docs

… ensuring tags which expect names per docs will be reported

Also ensures `see` tag with only an inline link tag is not treated as empty.