Well log plot: Parse Schedule section for WSEGLINK data

[hhgs]

When DATA-file is available, parse Schedule section recursively to identify all WSEGLINK keywords with data. New links are listed by well and segment-to-segment.

WSEGLINK well-name segment-no-1 segment-no-2 / . . . /

If item #2 and #3 are undefined, all segment links for the well are removed. If either item #2 or #3 is undefined, all segment links are removed for the well and segment given.