filehandlers.py:
    added a new LOFARdata_Pcombined filehandle which takes a list
    of subband files and 'concatenates' them together.
    So this class acts like a single file with lots of subbands
    The code currently doesn't make use of this class.
    I had to introduce a 'seek_record_read' routine to avoid
    lots of seeks since LOFARdata_Pcombined opens lots of files

fold.py:
   * removed 'dtype' argument since this is attached to the filehandle
   * catch exceptions on psrfits processing... this is still a work in
     progress