first handle all integer properties, then all double ones

this is required in situations where double grid properties depend on
the values of integer (i.e, *NUM) ones which appear later in the
deck. Example:

```
PROPS

SWU
* /

REGIONS

SATNUM
*2 /
```

the default value of the SWU keyword depends on the value of the
SATNUM property which only gets defined later in the deck. an
alternative to the approach of this patch would be to process the
grid properties of the REGIONS section before the others. I'm a bit
indifferent which approach is better...
Merge pull request #294 from andlaus/GridProperties_first_int_then_double

first handle all integer properties, then all double ones