simplified format used for biviewer link files

changed biviewer.py to accept a simpler format of the link file
previously had to convert from complex next of dicts, now is just a
list of dicts:
[{'cdsr_filename': cdsr_filename, 'cdsr_refcode': cdsr_refcode,
'pm_filename': pm_filename},....]
This will make it easier to apply filters and generate new link files
which look at subsets of the data, and enable future development of pdf
biviewers etc.
all biviewer_links pickle files regenerated in the new format also