Changes to use Moodle's qbank exporttoxml script instead of custom code (#192)

Coderunner had its own script to download the export of a single
question. But to avoid a lot of custom code and use standard Moodle
script, deleting the coderunner's exportone.php and using Moodle's
instead.

Author: AnupamaSarjoshi

exportone.php

@@ -77,7 +77,10 @@
 $qbankparams['lastchanged'] = $questionid;
 
 $questionbanklink = new moodle_url('/question/edit.php', $qbankparams);
-$exportquestionlink = new moodle_url('/question/type/coderunner/exportone.php', $urlparams);
+$exporttoxmlparams = $urlparams;
+unset($exporttoxmlparams['questionid']);
+$exporttoxmlparams['id'] = $questionid;
+$exportquestionlink = new moodle_url('/question/bank/exporttoxml/exportone.php', $exporttoxmlparams);
 $exportquestionlink->param('sesskey', sesskey());
 
 // Create the question usage we will use.