ox-odt: Use options instead of hard-coded variables

ox-odt: Use options instead of hard-coded variables

* lisp/ox-odt.el (org-odt-styles-dir,
  org-odt-create-custom-styles-for-srcblocks, org-odt-table-styles,
  org-odt-get-table-cell-styles): Fix docstring.
(org-odt-format-headline-function,
org-odt-format-inlinetask-function): Change default value.

(org-odt-template, org-odt-drawer, org-odt-format-headline--wrap,
org-odt-inlinetask, org-odt--enumerate, org-odt--image-size,
org-odt--enumerable-image-p, org-odt--enumerable-latex-image-p,
org-odt--enumerable-formula-p, org-odt-link, org-odt-table-style-spec,
org-odt-timestamp): Use option instead of hard-coded variables.

(org-odt-format-headline): Remove function.

(org-odt-do-format-code): Change signature.  Use options instead of
hard-coded variables.
(org-odt-fixed-width, org-odt-latex-environment,
org-odt-link--inline-image, org-odt-format-code): Apply signature
change.

(org-odt-format-headline-default-function,
org-odt-format-inlinetask-default-function): New functions.

(org-odt-link--inline-image): Fix indentation.