[BUG #7390] @type can have a descriptive text

- also fix "(opt.)" for other descriptive texts
[BUG #6968] fixing various @ignore hints
[BUG #7395] some preparations to add file and line numbers to JSDoc issues

- let Comment.parse return parse issues as entries, with corresp. 'error' attributes
- process those in the calling layer, where usually node information is available
  (so you can get at file name and line number)
- it would still give the line number of the code node, not the exact line number
  in the JSDoc comment :-(
- not working yet (try with want_errors=True)