Form_Basic: remove comment
Field_ValueList: add validate, simplify loadPOST
Field_Radio: remove comment, extend message
Field_DropDown: remove validate, add multi support

1) validate moved to ValueList
2) multiple value support
Field_CheckboxList: remove validate and loadPOST

1) validate moved to ValueList
2) loadPOST moved to ValueList
Merge pull request #233 from DarkSide666/patch-24

Multi value support for form fields etc.