I added that as a convenience method while working on implementing
multi-value filtering.  But we need to stick with the plural version
GetQueryItems() from now on for clarity.

We are still not 100% compatible, e.g. Excel's "show blanks" setting
is not cleanly mapped (partly due to ODF's limitation).  But that's
a future TODO.

+ IsValidDate() checks only day and month regarding the year, not Gregorian
  cut-off date as now does IsValidAndGregorian().
+ Normalize() carries over invalid day and month values to next months and
  years.
* All methods that return or internally use a day count now internally
  normalize the date values, without modifying the actual Date instance. So,
  if the date is not valid you may get unexpected results.
  * Previously, a date with month>12 would had accessed the days-of-month
    array out of bounds on all such methods. So you would had gotten
    unexpected results anyway..
  * Affected methods are:
    GetDayOfYear()
    GetWeekOfYear()
    GetDaysInMonth()
    static DateToDays()

* Read dates with years consisting of less than 4 digits.
  ISO 8601 specifies that years are to be written with a minimum of 4 digits.
  However, be lenient in what we accept.
* Write years < 1000 with leading zeros to comply with ISO 8601 YYYY.

Use the newly introduced Date::Normalize() instead of a never ending
while(!date.IsValid())

+ IsValidDate() checks only day and month regarding the year, not Gregorian
  cut-off date as now does IsValidAndGregorian().
+ Normalize() carries over invalid day and month values to next months and
  years.
* All methods that return or internally use a day count now internally
  normalize the date values, without modifying the actual Date instance. So,
  if the date is not valid you may get unexpected results.
  * Previously, a date with month>12 would had accessed the days-of-month
    array out of bounds on all such methods. So you would had gotten
    unexpected results anyway..
  * Affected methods are:
    GetDayOfYear()
    GetWeekOfYear()
    GetDaysInMonth()
    static DateToDays()

Once smaller than 1582-10-15 decrementing a Date will not produce a valid date.

- introduce first two basic tests (to be improved)
- rewrite of UpdateInformationProvider::load() to use comphelper
- smaller splitting of functions to be able to unit test

i.e.

mnOutWidth = maPaperSize.Width() - 2*maPageOffset.X();
mnOutWidth = maPaperSize.Width() - 2*maPageOffset.Y();

might possibly be intended to be

mnOutWidth = maPaperSize.Width() - 2*maPageOffset.X();
mnOutHeight = maPaperSize.Height() - 2*maPageOffset.Y();

either way, its behind a special getenv, so ditch the lot

sc/qa/complex/calcPreview/ tests do not work automatically and have been left
alone.