parsing fails when at least one column is a string

currently the parsing fails, when one column is a string.

we should decide whether we want to ignore columns that contain strings or whether we want to put them into database column result_str

ERROR:CsvParser:storing observation(s) failed for (0, 0), (0, 'SITE_CODE'): https://deims.org/8eda49e9-1f4e-4f3e-b58e-e0bb25dc32a6
ERROR:data-parser:parsing with parser='CsvParser' failed
Traceback (most recent call last):
  File "/home/appuser/app/extractor/parse.py", line 144, in <module>
    parse()  # pylint: disable=no-value-for-parameter
  File "/home/appuser/.local/lib/python3.9/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/home/appuser/.local/lib/python3.9/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/home/appuser/.local/lib/python3.9/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/appuser/.local/lib/python3.9/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/home/appuser/app/extractor/parse.py", line 124, in parse
    parser.do_parse()
  File "/home/appuser/app/extractor/Parser/CsvParser.py", line 146, in do_parse
    observation = Observation(
  File "/home/appuser/.local/lib/python3.9/site-packages/tsm_datastore_lib/Observation.py", line 30, in __init__
    self.check_value()
  File "/home/appuser/.local/lib/python3.9/site-packages/tsm_datastore_lib/Observation.py", line 34, in check_value
    if math.isnan(self.value):
TypeError: must be real number, not str
INFO:tsm_datastore_lib:Close database session.