Fix qualifier problem for pfold & sanitize epfold code

The epfold function relied on array_map/parallel_map to call pfold.
This does obviously not work for the "normal" input to pfold.
It was solved by having all the input parameters (except the period)
alternatively be passed as qualifiers. The new implementation missed
this for the time array. Now 't' is accepted as a qualifier.

Additionally, the code of epfold and epfoldpdot was reworked slightly.
No logic was changed except that errors are now properly raised as
exceptions and chatt/verbose uses the _Isisscripts_Verbose variable.