Create 'ncdc.station.data' function and validate input

Checking whether the inputs for starting year and ending year are correct. Removing hardcoded test years.
Define additional params for ncdc.station.data function

Adding option for using already-defined latlong bounds (from 'define.calmet.domain' function) or specify the bounds manually as a vector.
Validate whether data exists for function

A check made for whether the CALMET domain bounds exist. The parent function assumes data is there as a default option. Non-existance of this object stops the function.
Add closing brace to function

Encapsulating the new function.
Remove segment of function with hardcoded subsetting

Previous code made subset of station data for those just in US and Canada.
Add conditional for using predefined bounds

Control structure for selection of boundaries (for
station selection) implemented.