Please describe the problem:
The QIF importer remembers the namespaces and mnemonics that were entered for previously imported QIF securities, but this information is lost after importing to a new GnuCash file.

Steps to reproduce:
1. Make a backup your qif-accounts-map file, then remove the original.
2. Start GnuCash with --nofile.
3. Import the attached QIF file.
4. Notice that the mapping of the QIF security name to the GnuCash commodity's namespace ("NYSE") and mnemonic ("C") has been saved in qif-account-map.
5. Restart GnuCash, again with --nofile.
6. Import the same QIF file.


Actual results:
The qif-account-map still contains the QIF security name, but the GnuCash commodity's namespace and mnemonic have been lost (both are ""). The mapping is now completely useless.

Expected results:
The qif-account-map is unchanged.

Does this happen every time?
Yes

Other information:
This bug is related to bug 511006, but not a duplicate. 511006 is easy to fix and may be patched on its own, whereas fixing this bug requires a larger effort.