Add reader/writer as in csv module

[jferard]

reader = py4lo.reader(oSheet)
for row in reader:
    ...

reader = py4lo.dict_reader(oSheet):
for row in reader:
    ...

With fields: fieldnames, line_num, reader, restkey, restval

writer = py4lo.writer(oSheet)
writer.writerow(...)

writer = py4lo.writer(oSheet, fieldnames)
writer.writeheader()
writer.writerow(...)

With fields: extrasaction, fieldnames, restval

[jferard]

Done.