UDatePicker improvements

• UDatePicker improvements:
  • documentation added - see https://unitybase.info/api/adminui-vue/index.html#/Presentational/UDatePicker
  • panels for ranges are unlinked by default (month can be changed separately)
  • placeholder i18n for date range changed from Start Date - End Date to from - to ( з - по for uk)
  • added defaults shortcuts. For date - Today and Yesterday, for range Today, Yesterday and "current month"
• FTS widget and "range" date filter for 'UTable' uses u-date-picker with all options is default
• UAutoFiled for Date and DateTime sets u-date-picker clearable to false for attributes what do not allow nulls