support integer arrays in tables

since r4777, `get_table_column` can be used to retrieve integer table columns. Currently, these are ignored, since I didn't realize that type=1 means integer array in this case as well.
Since this function is quite small, we could just add the corresponding C-code to the libmadx.pyx module instead of requiring an updated MAD-X library.

I can implement this, when I have some spare time.