Make marble, ICU and SQLite optional

Once the textshape starts using calligradb,
it'll have to be disabled if we cannot build
calligradb because of a missing icu, but there
is no reason to stop people from building the
other parts of calligra.

The previous way of disabling was done with a
IF(CREATIVEONLY) block, but that hides the variables
and makes everything fail in creativeonly mode.