MLW: Improvements for multiple completion data in same grid block

[magnesj]

Several improvements has been covered in #7049. Improvements described here require substantial rewrite of code.

For a multi-lateral well where two or more laterals are completed in the same grid block:

If MSW-export, for COMPSEGS(L) define:

• Branch number for I/J/K-block equal to well branch with largest Tr-value

If WSEGVALV is present

• use Tr-weighted flow coefficient (item#3)

If WSEGAICD is present:

• use Tr-weighted average strength of AICD (item Enable builds in the development tree without cluttering Git's status #4).