Make ServiceBinding immutable

[Rick-van-Dam]

Currently some fields in ServiceBinding are mutable. This has some disadvantages:

• It could cause hard to understand problems when reusing the same ServiceBinding instances across containers.
• If ServiceBindings are immutable there is a possibility to turn this class into a struct for less memory usage (needs more research).

A possible solution would be to split the immutable and mutable part of ServicBinding into 2 different concepts.