Add time series property for StateMod reservoir targets time series

[Steve Malers]

The StateMod reservoir target file *.tar has two time series per reservoir for minimum and maximum target. However, the are not uniquely identified so that other code can differentiate. Need to add a time series property so that they can be uniquely identified later and the property used for filenames, etc.

[Steve Malers]

I added the property and tested in TSTool using the property to define a data type and filename. Close the issue.