Improve list handling callback javascript code

[Nicklas Nordborg]

While working with #1962 it became apparent that there are lots of very similar methods for handling callbacks after selecting a related item in an edit dialog. For example, after selecting a protocol for a sample:

samples.setProtocolCallback = function(event)
{
  var frm = document.forms['sample'];
  var list = frm.protocol_id;
  if (list.length < 2 || list[1].value == 'NaN')
  {
    Forms.addListOption(list, 1, new Option());
  }
  list[1].value = event.detail.id;
  list[1].text = event.detail.name;
  list.selectedIndex = 1;
}

It should not be too difficult to create a generic callback that can replace more or less all existing implementations. Typically the only difference between the various functions are:

• The name of the form and input field, but we can get this with event.currentTarget.
• If the option should be inserted at index=1 or index=0. This depends on if there is a 'none' option or not available.
• In some cases there is an additional call to a 'onclick' or 'onchange' method. It is better to implement this by sending a real 'onchange' event.

[Nicklas Nordborg]

(In [7001]) References #1963: Improve list handling callback javascript code

Added Items.onItemSelected callback handler that can be attached to 'base-selected' event. The handler will insert or update the list it is attached with the item information sent in the event. If the new information is different from the currently selected a 'change' event is firef.

Most old event handlers should now be replaced with the new handler.