Support bodyParam attribute without form parameter name to map the whole body to a single parameter

[s-ludwig]

Should be supported for the web and REST interfaces:

struct S { int foo; string bar; }
@bodyParam("s") void postFoo(S s) {}

For the web interface generator, this means that the endpoint "POST /foo" accepts two form parameters, "foo" and "bar". The REST interface generator instead expects a JSON object of the form {"foo": ..., "bar": ...}.

[s-ludwig]

In particular, this means that the struct/class members are treated just like the parameters of the method usually are. The initial incarnation of this feature supports only structs/classes.