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 validate, use caution

![screenshot_2013-10-15-01-13-56](https://f.cloud.github.com/assets/4014433/1332223/582be174-3575-11e3-8e28-3f5766722fe9.png)

- 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.
![screenshot_2013-10-15-04-05-50](https://f.cloud.github.com/assets/4014433/1332228/6db179d2-3575-11e3-9f5d-c884d1ea5b4e.png)

![screenshot_2013-10-15-04-05-57](https://f.cloud.github.com/assets/4014433/1332230/7ab9e628-3575-11e3-828d-6e9b7632ee3f.png)