ox-bibtex: Port for "org-exp-bibtex.el"

* contrib/lisp/ox-bibtex.el: New file
ox-taskjuggler.el: Fix byte compiler warnings

* ox-taskjuggler.el (org-taskjuggler-get-project)
(org-taskjuggler-resolve-dependencies): Fix references to free
variables.
ox-taskjuggler: Small fix

* contrib/lisp/ox-taskjuggler.el (org-taskjuggler-assign-task-ids):
  Small fix.
org-element/ox: Fix src-block indentation when it should be preserved

* lisp/org-element.el (org-element--remove-indentation): New function.
(org-element-example-block-parser, org-element-src-block-parser): Use
new function.
(org-element-src-block-interpreter): Update function according to
change.
* lisp/ox.el (org-export-unravel-code): Do not remove any indentation
  since it now happens at the parser level.
* testing/lisp/test-org-element.el: Add tests.
* testing/lisp/test-ox.el: Refactor tests.
Merge branch 'maint'
org-element: Fix a docstring

* lisp/org-element.el (org-element--remove-indentation): Fix
  docstring.
Merge branch 'maint'
org-element: Small optimization

* lisp/org-element.el (org-element--remove-indentation): Small
  optimization.
Merge branch 'maint'
org.el (orgstruct-setup): Bind all intermediate key translations.

* org.el (orgstruct-setup): Bind all intermediate key
translations.