Added additional Unicode alternatives, added tests

[ahelwer]

• Nat, Int, and Real can now use the alternative ℕ, ℤ, and ℝ symbols respectively
• Converted primitive_value_set node to a supertype, added nodes for each primitive value set type
• Fixed not specifying : and → as right delimiters in external scanner
• Added additional tests for CASE construct, including Unicode tests
• Added tests of ], →, and : as right-delimiters for jlists
• Bumped minor version number