[Kst] Combine date / time columns to one x-axis

[Nicolas Brisset]

>   - use "Time Format" dd.MM.yyyy; hh:mm:ss;
Why the second semicolon?
I had tried this, but with only one semicolon in the middle. 
We never take care about separators in other cases.
Couldn't we:
- replace the separator with a space
- simplify spaces
and then read the string and interpret it?
It would have the benefit that one or more spaces would work, at the cost of some extra processing. 
Right now we have this hard-coded:
if (*(p + end) == ' ' || *(p + end) == '\t')
which I feel a bit uncomfortable with...

Nicolas