Handle case where description field is not imported

If description field is not imported it ends up being empty causing the
core apis to complain.  The fix to detect this scenario and set the
description to value imported for summary.
Added users should have valid email addresses, random password, and disabled

It is important to not create non-secure user accounts as part of the csv
import.  Before this change an account was created with empty email,
and user name as the password.  The change sets the email to a valid address,
sets a random password, and creates the account as disabled.  Administrators
can then go an re-enable / reset password if needed.
Default to 'ignore_column' when column name doesn't match a known column.
By default import as new issues rather than match by ids.