Sort payments by Fund Name

Currently the payments are retrieved and displayed in "database order",
which is indeterminate. This commit tells the database to retrieve them
sorted by the fundName column, which makes the display more usable.

Signed-off-by: Remington Steed <rjs7@calvin.edu>
Simplify date checking with new function is_null_date()

Factor out null date checks ("0000-00-00" or "") into a new function.

Signed-off-by: Remington Steed <rjs7@calvin.edu>