GMPLS update - 37: adding in-segment create/remove API

Added #in-segment #create / #remove routines in GMPLS module. These #routines #handles the #hierarchical dependency between the different variants of in-segment configuration #entries. On creating the #standard #in-segment entries they automatically creates the in-segment #statistics entries, in-segment #standard #GMPLS entries and in-segment #extended #custom entries as well. On removing the standard entries the related entries also will be removed.

#GMPLS update 37 ...
[commit afd902fa3a555dc4074316b6916788ea32712800] (https://github.com/nes-repo/NES-Open-Switch/commit/afd902fa3a555dc4074316b6916788ea32712800)