Inheritance support

[hauke96]

Add support for the two types of inheritance: Type- and implementation-inheritance.

For type inheritance add the keyword "inherits": "SomeOtherClass". This will create actual inheritance in the code (as far as it is supported) which will produce this kind of json when transmitted:

"field": "value",
"otherField": "otherValue",
"SomeOtherClass": 
{
  "someOtherField": 123
}

For implementation inheritance add the keyword "embed": "SomeOtherClass". The generated code will then produce this kind of transmitted json:

"field": "value",
"otherField": "otherValue",
"someOtherField": 123

It simply embeds the field of SomeOtherClass.