add wrapper for `org-export-as 'html` to avoid repeating settings

[titaniumbones]

cf. line 1443 of org-lms:

 (let* ((org-export-with-toc nil)
         (org-export-with-smart-quotes nil)
         (org-html-postamble nil)
         (org-html-preamble nil)
         (org-html-xml-declaration nil)
         (org-html-head-include-scripts nil)
         (org-html-head-include-default-style nil)
         ;;(atext (org-export-as 'html t))
         (atitle (nth 4 (org-heading-components)))
         (org-html-klipsify-src nil)
         (org-export-with-title nil)
         ;;(courseid (plist-get course :id))
         (atext (org-export-as 'html t nil t))
         (response nil)
         (oldid (org-entry-get (point) "ORG_LMS_ANNOUNCEMENT_ID"))
         )
         ...
         )

let's move all those to a wrapper and start filtering some of them out.