Add setting to preserve leading zeros

A setting to preserve leading zeros is essential when working with CSV files. I work with account numbers which often include leading zeros and are are not a fixed length. As such, any work-arounds to pad leading zeros to a fixed length value do not work. Rather, I prefer if the application did not corrupt data upon opening a file in an attempt to be "helpful". A global setting to preserve leading zeros, which would allow files to be opened from the file manager without corruption would be fantastic.

No files or tests are named. Start by locating the CSV opening and parsing entry points, then trace where numeric-looking account values lose leading zeros. Done means a global setting can preserve arbitrary leading zeros when files are opened from the file manager without requiring a fixed field length.

Written by the indexing model from the issue text.