surpress error messages when running in groupby or in loop

[naurisozols]

add possibility to set false on error messages when running functions in loop or using Pandas groupby.. In case of error - no value returned (empty), but it's not affect further workflow execution

[Anexen]

Hi, @naurisozols. Added the ability to silence the exception in version 0.7. Please try xirr(..., silent=True)