readucn: Read MT3DMS .ucn File
In dpphat/MFtools: This is a package for reading MODFLOW and MT3DMS files

This function reads in a binary ucn file and creates a data frame composed of the following elements:

1	readucn(ucrootname, NLAY, NTTS)

`NLAY`	This is the number of layers assigned to the model
`NTTS`	This is the number of transport time steps that are printed to the .ucn file. This can be obtained from the .btn file. This will cause an error if the value assigned is greater than the correct value. Future versions will need to be developed so that NTTS is not needed for this function to operate properly.
`ucname`	This is the name of the ucn file