Added ability to expand variables in body annotation and expand request line variables 

Example below serialises complex type "Operation" into the inputData placeholder in @Body.
 
```java

@RequestLine("POST /sdpapi/request")
@Body("OPERATION_NAME=GET_REQUESTS&TECHNICIAN_KEY={technicalKey}&INPUT_DATA={inputData}")
    public API getRequests(
        @Named("technicalKey") String technicalKey,
        @Named("inputData") Operation operation
    )

```

The example below automatically expands the key-value pairs for the fields variable.

```java
@RequestLine("PUT /1/cards/{cardIdOrShortLink}?key={key}&token={token}&{fields}")
    public Card updateCardWithFields(
        @Named("key") String key,
        @Named("token") String token,
        @Named("cardIdOrShortLink") String cardIdOrShortLink,
        @Named("fields") Object fields
    )
```