GMPLS interface update - 2: added MPLS interface external API

Added #MPLS-interface #external #API routines in GMPLS module. This enables to #create / #remove #MPLS-interface related #hierarchical #entries through a single API. The standard GMPLS interface entries are also created indirectly through these routine calls. The MPLS interface handle will be using these routine calls to create the MPLS-interface as the side effect of creating the corresponding logical-interface in the IF module. The MPLS interface entries #contain the #attribute s like #current range of #in-coming / #out-going #label s used and the #bandwidth #state.

#GMPLS update 11 ...
[commit e5076ee24e302a0366167704cfc6fd04abce9fc1] (https://github.com/nes-repo/NES-Open-Switch/commit/e5076ee24e302a0366167704cfc6fd04abce9fc1)