org-element: Store keywords in upper cases

org-element: Store keywords in upper cases

* EXPERIMENTAL/org-e-ascii.el (org-e-ascii-keyword): Apply keywords
  case change.
* EXPERIMENTAL/org-e-html.el (org-e-html-keyword): Apply keywords case
  change.
* EXPERIMENTAL/org-e-latex.el (org-e-latex-keyword): Apply keywords
  case change.
* EXPERIMENTAL/org-e-odt.el (org-e-odt-keyword): Apply keywords case change.
* contrib/lisp/org-element.el (org-element-export-block-parser):
  Internally store type in upper cases.
(org-element-keyword-parser): Internally store keyword `:key' property
in upper cases.
(org-element-non-recursive-block-alist,
org-element-affiliated-keywords,
org-element-keyword-translation-alist, org-element-multiple-keywords,
org-element-parsed-keywords, org-element-dual-keywords):
Use uppercased keywords.
(org-element-current-element): Use uppercase for keywords.
(org-element-collect-affiliated-keywords): Store affiliated keywords
in upper cases.
* contrib/lisp/org-export.el (org-export-get-inbuffer-options,
  org-export-collect-tree-properties, org-export-resolve-fuzzy-link):
  Use upper cased keywords.
* testing/lisp/test-org-export.el: Update tests.