MODULES:LN_GLGUI: Fixed the date picker and date wheels bug.

- Bug caused limits from the previous value to still be applied when 'value parameter set to something new.
- New parameter 'unlimited set to true by glgui-datepicker-unlimited/glgui-datewheels-unlimited and set back to false by glgui-datepicker-update-limits/glgui-datawheel-update-limits
- Setting the 'value, 'datemin or 'datemax when unlimited set to #t no longer changes available values in the pickers/wheels, but if 'datemin or 'datemax set, the value itself is modified if necessary to fit in the range.
- glgui-datepicker-update-limits and glgui-datawheel-update-limits no longer return the corrected value from the limits being applied, instead directly fix the 'value to be within the limits.
- date picker and date wheels handle the 'value being set to #f without crashing.