BUG: Lookup Function imports values that are clearly numbers in a CSV as strings

[dzwillia]

Describe the bug
Using a CSV file with number columns as the source for a lookup task will import those columns as strings.

To Reproduce
Steps to reproduce the behavior:

1. Download these CSV files and save them to Dropbox (these files can also be found in Dropbox (Flex Research) > temporary > github-issues > flexiodata-flexio > 579
2. In the web app, go to Functions
3. Click New > Extract Function
4. Save the function
5. Select one of the CSV files from the above ZIP file as your lookup file
6. Select "company" and "stage" as your key fields
7. Select "tot_deals" and "tot_value" as your return columns
8. Save the function

Expected behavior
If you test this function in the app, it works, because the "stage" test value is a string. We would expect it to work in Excel of Google Sheets then as well. However, open Google Sheets and try to that function with the "stage" parameter as a number and it will return nothing.

Screenshots

Additional notes
There are likely multiple things going on here -- 1) the lookup import was done pretty quickly and should probably do better type checking so that the columns are typed better. 2) The function execution should probably be a little more forgiving on type matches or something. Dunno -- maybe, maybe not.