added special case to MC for html

- imported items save the entire html in the xml file, and when
displaying questin, the html (will be) displayed
- fixed addItem (copying item) to fix the img src links in the html
string when copying item

- need to add code to display the html in itemMC and questionFuncsMC
- need Vasily to modify converter to differentiate stem from the rest
of item body to not include it in the html string