Flag not processed wel by camels forcing

[Daafip]

Currently camels USA files are supported by HBV forcing.

This functionality should become part of eWaterCycle in future and was mostly done for the purpose of my thesis.
Some streamflow files include flags to show values are estimated A:e, or missing M. These aren't processed properly by the pd.readfwf function currently used. See readme in the dataset for more info:

An example is 08178880_streamflow_qc.txt.

todo:

• properly read files with flags
• add the flags to the netcdf file created

[Daafip]

excerpt from readme_streamflow.txt obtained from https://dx.doi.org/10.5065/D6MW2F4D

  The files have no header with five columns of data:  GAGEID Year Month Day Streamflow(cubic feet per second) QC_flag
  Streamflow data that are missing are given the streamflow value -999.0

  The files are daily mean streamflow, so the hour is always just set to 0.
  The QC flag is a string and can have to values: "A","A:e", "M"
	A   -> streaflow value is certified by USGS as the actual daily mean flow
	A:e -> streamflow value is certified by the USGS as the actual ESTIMATED daily mean flow
        M   -> streamflow value is missing from USGS record