Adding null-based operators to the expression language

[Yuri-Blankenstein-TNO]

This issue adds support for the following expressions:

• Null Coalescing operator (i.e. a ?? b)
• Ternary Conditional operator (i.e. a ? b : c)
• Null safe expression chaining (i.e. a?.b?.get(c))
  TODO: Investigate if this is feasible