Validate DESIGN2PARAM configuration at start up instead of when running forward model

[eivindjahren]

Currently the following failures occur when you run the forward model (present in our logs). They should be
validated when the config is read:

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Provided realization arg 299 does not exist in design matrix

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Traceback (most recent call last):
File "../bin/design2params", line 8, in <module>
sys.exit(main_entry_point())
File ".../lib64/python3.8/site-packages/semeio/forward_models/scripts/design2params.py", line 77, in main_entry_point
design2params.run(
File ".../lib64/python3.8/site-packages/semeio/forward_models/design2params/design2params.py", line 53, in run
default_df = _read_defaultssheet(xlsfilename, defaultssheetname)
File ".../lib64/python3.8/site-packages/semeio/forward_models/design2params/design2params.py", line 317, in _read_defaultssheet
if paramname != paramname.strip():
AttributeError: 'float' object has no attribute 'strip'

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File .../input/distributions/design.xlsx is probably not of correct type. Failed with exception 'Worksheet named 'ETC' not found'

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WARNING - Design matrix contains empty cells [...]

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argument xlsfilename: .../input/designmatrix/design_matrix.xlsx is not an existing file!

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Design matrix not valid, error: Column headers not present in column: ...

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Column header "X " contains initial or trailing whitespace.

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design2params: error: argument realization: invalid int value: 'not_int'

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File .../ert/model/../input/designmatrix/design_matrix.xlsx not found