Feature: allow to ingest numeric when formatted with the percentage symbl

[jflairie]

Is your feature request related to a problem? Please describe.
When importing a column with numerical values formatted like 80%, the import will fail when you declare this column as numerical. As of now, we need to transform it to 0.8 to make it work. While understandable from a technical standpoint (everything is read as a string before conversion), this can be less convenient for end-users: in some cases 80% is more readable than 0.8

Describe the solution you'd like
When a column is specified as numerical, the import should work for values formatted with a % symbol

[bastienboutonnet]

Good one. Gonna have to see if:

• is it still a problem as of >=1.0.0 since I handle data type casting on the dataframe directly rather than let the db do its thing.
• given that we can control this earlier in this new version, would the percent signs be an issue?
• if so, would we want to support a light enforcemt whereby if (and only if) you specifically ask for a datatype we would throw away special chars, round stuff etc.