..F....... [ZBX-8832] Fix errors when POST has too many variables (more than allowed by max_input_vars in php.ini).
- Implement new request parameter input type T_ZBX_JSON and add unit test for function check_type().
- On client side - create global JsonParser instance that is used for converting to and from JSON and update code to use it instead of Object.toJson() and JSON.parse().
- Implement jQuery plugin "setJsonOnChange" that takes value of input or select, converts it to JSON string and sets it as value of some other input element. 
- Attach "setJsonOnChange" jQuery plugin to all elements having "data-serialize-to-hidden" attribute.
- Implement method CComboBox::serializeToVar(). Calling this method adds attribute "data-serialize-to-hidden" and it gets picked up by "setJsonOnChange" plugin. 
- Update user group permission view and controller to use CComboBox::serializeToVar() and make other improvements related to date exchange between server and browser.
- Improve CTweenBox:
  - Internaly CComboItem instances are used to represent items on either left or right side. 
  - All output HTML now is generated only when CTweenBox::get() is called.
  - All items on both sides are sorted by item captions on output.
  - Selected value (items on left side) now are set with CTweenBox::setSelectedValues() and not from contructor.
  - Items are added using CTeenBox::addItem() and do not affect selected values at all.
  - Improve JavaScript function moveListBoxSelectedItem() to use values of options in left multiselect.
- Update current uses of CTweenBox to new interface.