Allow SelectionSet to be defined during method call

[fabiocarvalho777]

Currently the custom selection set can only be defined during client API definition time (statically set with SelectionSet annotation in the GraphQL operation method). However, sometimes applications might need to set custom selection sets per method call. In order to support this use case, SelectionSet annotation can be enhanced as follows:

1. SelectionSet annotation should be modified to be applicable to method parameters as well.
2. Mocca should recognize the presence of a String parameter annotated with SelectionSet in the GraphQL operation method, and use it to define the selection set.
3. A MoccaException exception should be thrown in the following cases:
   1. If SelectionSet is present at both method and parameter level
   2. If SelectionSet annotated more than one parameter
   3. If the SelectionSet annotated parameter is not a String
   4. If SelectionSet ignore field is set when used to annotate a String parameter

Important note

Similarly to when applying SelectionSet to the return type, but defining it statically as a String, if the custom selection set defined in the parameter does not match the return type, then an exception should be thrown. Developing this behavior is out of scope for this story, as it is already implemented. However, negative tests should be added to exercise this situation.

Acceptance Criteria

1. Use case described above is implemented
2. End user document is changed accordingly
3. Javadocs are changed accordingly
4. Unit and/or functional tests are added
5. Make sure to add negative tests as well