Necessary changes which goes together with MatrixBox

• LabelField display errors outside of <label> tag because in case of rendering with {label: false} one could not see errors (bugfix)
• FloatField does make distinction between empty string and 0 (shows the correct value) (bugfix)
• FloatField receives "input_format" from ERP5 and handles correctly percentages (shows % symbol and multiply by 100 every time) (bugfix)
• MatrixBox subfield checks its value using external_validator modified ERP5Form/MatrixBox.py (bugfix)