For integer valued variables, tracer produces too many tick marks & labels

[bredelings]

If I look at a variable with integer values between 0 and 1000, tracer will produce 1000 tick marks. The main problem is that the labels for the tick marks are drawn on top of each other.

This worked fine before tracer tried to use different methods of drawing tick marks for integer variables, but now the axis labels for integer values are more or less unreadable.

One approach would be to fall back to the old way (i.e. for continuous variables) if the range contains more than 50/100 integer values.

[rambaut]

For discrete axis, the aim was to show all values but this should only be for when there are less than a certain number of states.