add support for assigning values to sets with value list notation

Submitted by Kristof Szabados

Description

In the current version of the TTCN-3 standard it is possible to assign a value to a set typed definition using value list notation. This method is not yet supported by Titan.

According to the standard it should work like this: "When the value list notation is used for values of set types, the values are assigned to the fields in the sequential order of the fields in the type definition. " from section 6.2.2.0 of v4.12.1 of the core standard

Version: 6.6.1