- Change german phrases to english
- Bugfix temperature

- Modify the calibration constants to include the fullscale value
  (M=40 for manual calibration; M=42.5 for self-calibration)
- Allow different channels with different calibration method
- Read calibration mode and temperature from saved calibration

- Manual calibration added
- Calibration functions cleaned and updated

- Add data points (NaN) when gap is longer than filter block
- This guarantees continuous timeseries in 1 Hz output

- set_msec to set milliseconds
- add_time to add a time difference in sec/nsec
- bugfix when assigning data
- initiialize with zero time and missing data value

- Separate pointers for reading and writing
- Overwrite read() and write() routines

- Filter was also applied when no appropriate filter available

- Create map to store filter values of different size

- filter_fir_sym_time is removed
- median_time is used for filter_fir_sym
- median_time needs to be updated to use average with even
  number of samples (TODO!!)
- median_time made public to allow setting timestamp without
  filtering the data

- buffer_obs_file was introduced as base class
- buffer_obs_file_ascii for writing ascii files
- buffer_obs_binary for binary files
- At the moment, data type for binary is fixed:
  - POSIX time (from struct tm)
  - Vector data as float
  - No supplementary data
- Note that size of files depends on machine, i.e.
  size of datatype

Buffer was dynamically allocated based on first entry of data type.
In case the second entry (e.g. Y) was larger, it was truncated.