add warnings to Serials.pm

add warnings to Serials.pm

Change obvious warning generators:
     ( use of string comparisons in numeric comparison)
     ( declaration of variable in comnditional )
also some errors caused by undefined values:
    abouttoexpire was not checking for undef values
    Pass a valid planneddate in generation of next expected
    (undef here causes odd results)
Add a basic test script
    test is minimal but I fell over a bug this would have caught