Parameters: fix #225, localization, validation and list selection of known values

Parameters:
- fix for #225, fractions and signed values accepted as expected
- localization of decimal and grouping separators should work
- edited values are validated using range or set of valid values from metadata if available.
The colour of the edited value is changed to reflect the outcome
GREEN - valid
RED - invalid
YELLOW - could not be validated, use caution


-added an [ Edit ] to the parameter info dialog if set of known values available in metadata to allow the operator to choose a value for simple, bulletproof editing.