Add command line setting for NUM_CYCLES in monitor plot scripts.

[EdwardSafford-NOAA]

Modify the RadMon, OznMon, adn ConMon plot scripts to add a command line option to set the number of cycles in a plot. This would apply to the time series plots only and would override the default value of NUM_CYCLES, setting it to the input value.

The NUM_CYCLES has a default setting in the parm/*Mon_user_settings or parm/*Mon_config file, but at times it's useful for certain experiments to be plotted over longer spans than others. This is particularly true for the RadMon but it will be potentially useful to the OznMon and ConMon as well.

The MinMon does not produce time series plots, so it won't be modified.

[EdwardSafford-NOAA]

Closed via PR #39 .