[cpp] pass arguments as const reference

[MartinDelille]

Description

Passing arguments as const reference would allow developer not caring about memory issues and would reduce the generated code.

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Suggest a fix/enhancement

#264 #270 #273

[etherealjoy]

I would add here in general also the handling of setters for complex types

[stkrwork]

This issue relates to that #273

[MartinDelille]

To #270 too

[etherealjoy]

I applied this to the Qt5 server, but for the client we have to rewrite the helpers since the serialization is dependent on the pass by pointer.

I applied this to Pistache based on @stkrwork initial changes.