WebBasket: many small fixes and improvements

• Replaces various dblayer functions that would return faulty values due to GROUP_CONCAT with improved versions of them. Improves handling and parsing of the values returned by the dblayer functions to create the main WebBasket interface. Removes all calls of the eval() function and replaces them with safer functions. Sanitizes user input coming fromthrough GET and POST variables. Sanitizes special HTML characters like '&'. (closes #879)

• Improves creation of HTML Select form elements to be compatible with all major browsers. (closes #878)