Hydpy

*HydPy* now checks for missing values in e. g. meteorological input time series data. This behaviour can be enabled/disabled by setting option *checkseries* to True/False.

Additionally, XML file implementations of the XML schema file *config.xsd* are now easier to maintain regarding version changes and general options like *checkseries*.

From now on, installing `matplotlib` is not required for using (most features of) `HydPy` anymore.

For convenience, XML namespaces are now valid download links, and some name discrepancies result in warnings only instead of errors.

One can now manually define the name and style of log files when executing workflows based on XML configuration files.

From now on, version specific XML schema files will be part of each new HydPy release, making referencing them more comfortable.

These changes do not fix actual bugs but simplify coupling with Delft-FEWS.

Read from and write into flat archives, e.g. `LahnHBV/conditions/init_start.zip/land_dill.py` instead of `LahnHBV/conditions/init_start.zip/init_start/land_dill.py`.

This change does not fix an actual bug but simplifies coupling with Delft-FEWS.

hstream_v1` calculated `nan` values for some configurations. This should now be fixed.

We now perform proper integration testing for `hstream_v1`, so that this problem should not recur.