variable grid for the minutepicker

in my project I had the need to modify not only the minuteStepping, but also the stepping in the minutepicker because the stepping of 3 was too small.

my first intention was to use the minuteStepping parameter instead of the hardcoded value, but I think there might be the need for using individual values here. so i added minutePickerGrid to customize the stepping to whatever is desired.

since the possible grid sizes would damage the layout of the table, I had to modify the algorithm there to count up to 60 minutes and if there is place left in the table, it fills up the rest of the tablerow with empty cells.

thx in advance.