Sanity check data before start of processing

[tiadams]

Check data for possible issues like:

• Wrong/ non aligning column names
• Malformed/non-symetric structure of tables
• Too many data points (that may potentially break the frontpage due to timeouts)

Return appropriate warnings when the data is not in a salvageable format and do not start the processing if triggered. Also think about subsampling data if the provided tables are to big (e.g. only process 1000 random rows)