List also file annotation.
Added two functions.

  * lisp/pdf-annot.el (pdf-annot-put): New function for getting
    display-relevant edges. New function for getting the type.

  (pdf-annot-equal, pdf-annot-delete, pdf-annot-create-hotspots
  pdf-annot-show-annotation, pdf-annot-add-annotation
  pdf-annot-compare-annotations, pdf-annot-list-create-entry
  pdf-annot-list-goto-annotation, pdf-annot-at-position): Use new functions.
Skip unrelated buffers when activating the package.

  * lisp/pdf-tools.el (pdf-tools-install): Check for buffer-file-name.
Fixed a bug when running pdf-annot-inhibit-modification-hooks.

  * lisp/pdf-annot.el (pdf-annot-run-modified-hooks): Use cl-member with car.