Terminal support (FMI3, SSP2?)

There is a need to group signals into terminals in a portable way. The FMI3 (also supported in later versions of FMI2?) should cover this, an example is available #1418 . @arun3688 can you have a look at supporting terminals? There is not yet full support of Terminals in SSP but we should discuss a prototype implementation to aid in advancing SSP 2.0 to SSP 2.1 