qc_auto now supports multiple EC measurement heights used to calculat…

[ARibecaJob]

…e storage with the discrete approach.

Previously, only the first height specified in the file's "htower" field
was used to calculate the storage with the discrete approach.
qc_auto now supports multiple EC measurement heights, which may result
from changes in the setup, for example, to track canopy height growth,
even within the same year (e.g. in the case of crops).
The calculation of FCSTORTT, which may be used to derive NEE in case a
proper storage measurement is missing, now is based on all heights
specified in the file's "htower" field and the respective dates.

The following checks are added:

• The time resolution must be either half-hourly or hourly.
• The first timestamp must be YYYY01010030 for half-hourly data and
  YYYY01010100 for hourly data.
• The timestamps must fall within the year of the file.
• The timestamps must be in progressive order.