New type for "dynamic type" declarations

[oxisto]

For languages that do not have static types (such as JavaScript and Python), we probably need a distinct new Type, especially for declarations. The existing types do not really match this dynamic type.

• UnknownType should only be used for nodes whose type information are not available (yet). This is the default for inferred nodes or for nodes where we only can parse type information at a later stage and need to set "some" unknown type at the point of creation
• AutoType might be close to it, but this is used for scenarios where the compiler knows the exact time at build time, but the developer is too "lazy" to explicitly write the type. Examples includes C++ auto keywords or snippets like var a = "test" in Go. Basically, it can only be used for variable declarations, which have an initializer because type information is used from it.

A simple example to illustrate it in Python:

a = "test"
a = 2

In line 1, we create a new VariableDeclaration (in a pass) and the line represents an assignment to the Reference a. Currently, we set the type to unknown.
In line 2, we only have an assignment to a. The type of the reference to a can be inferred to int. The type of the variable declaration is not really determinable, but the assignedTypes could be set to int and str.

In the current implementation, we have the following problem:

1. Since the type of a is unknown, it will get the type of the first assignment, and after translation, the type of variable a is str and assigned types is str. This is incorrect
2. The type of the first ref is str and assigned types are str. This is ok
3. The type of the second ref is str (probably propagated from the variable) and assigned types are str, int. This is also incorrect.