org-agenda: Filtering in the agenda on grouptags

org-agenda: Filtering in the agenda on grouptags

Filtering in the agenda on grouptags filter also subcategories.
Exception if filter is applied with a (double) prefix-argument.

Filtering in the agenda on subcategories does not filter the "above"
levels anymore.

If a grouptag contains a regular expression the regular expression
is also used as a filter.

* lisp/org-agenda.el (org-agenda-filter-by-tag): improved UI and
  refactoring.

  Now uses the argument arg and optional argument exclude instead of
  strip and narrow.  ARG because the argument has multiple purposes
  and makes more sense than strip now.  The term narrowing is changed
  to exclude.

* lisp/org-agenda.el (org-agenda-filter-by-tag-refine): name change in
  argument to match org-agenda-filter-by-tag.

* lisp/org-agenda.el (org-agenda-filter-make-matcher): new optional
  argument EXPAND and refactoring.

* lisp/org-agenda.el (org-agenda-filter-make-matcher-tag-exp): new
  function, previously baked into org-agenda-filter-make-matcher.

* lisp/org-agenda.el (org-agenda-filter-apply): New optional parameter
  EXPAND, used in call to org-agenda-filter-make-matcher.

* lisp/org-agenda.el (org-agenda-reapply-filters): Uses another
  parameter (the new optional one) in call to org-agenda-filter-apply.

* lisp/org-agenda.el (org-agenda-finalize): use of new parameter in
  call to org-agenda-filter-apply.

* lisp/org-agenda.el (org-agenda-redo): Use of new parameter in call
  to org-agenda-filter-apply.