Double quote support for SUMIF() condition

SUMIF() condition can have double quote, such as '=SUMIF(A2:A4,">""",B2:B4)'.
This formula purpose is to compare the character double quote (").

In our previous patch (commit f1a1f525) we wrongly assumed that
PHPExcel_Calculation_MathTrig::SUMIF() expected the condition to escaped ('>""'),
but this is actually not the case in real use of PHPExcel, so the unit tests were
modified accordingly to use non-escaped condition ('>"').
Merge pull request #305 from PowerKiKi/fix_SUMIF_condition_including_double_quote

Double quote support for SUMIF() condition