Add protobuf tutorials

[pepone]

This PR adds Protobuf tutorials, fixes #387

[ReeceHumphreys]

I think that the Slice tutorial should go first here. Also I think it does seem a bit cluttered and hard to parse since the titles are so similar. Maybe we should renamed Tutorial to Slice Tutorial and then have a second Protobuf Tutorial category like in my example below?

Thoughts @externl @bernardnormier

Slice Tutorial
|-- Writing your First Server application 
|-- Writing your First Client Application
Protobuf Tutorial
|-- Writing your First Server application 
|-- Writing your First Client Application

[bernardnormier]

I think that the Slice tutorial should go first here. Also I think it does seem a bit cluttered and hard to parse since the titles are so similar. Maybe we should renamed Tutorial to Slice Tutorial and then have a second Protobuf Tutorial category like in my example below?

Thoughts @externl @bernardnormier

Slice Tutorial
|-- Writing your First Server application 
|-- Writing your First Client Application
Protobuf Tutorial
|-- Writing your First Server application 
|-- Writing your First Client Application

These are all IceRPC tutorials, not Slice tutorials or Protobuf tutorials.

[ReeceHumphreys]

I think that the Slice tutorial should go first here. Also I think it does seem a bit cluttered and hard to parse since the titles are so similar. Maybe we should renamed Tutorial to Slice Tutorial and then have a second Protobuf Tutorial category like in my example below? Thoughts @externl @bernardnormier

Slice Tutorial
|-- Writing your First Server application 
|-- Writing your First Client Application
Protobuf Tutorial
|-- Writing your First Server application 
|-- Writing your First Client Application

These are all IceRPC tutorials, not Slice tutorials or Protobuf tutorials.

Something like this then? Titles aside, I was asking more about this structure / hierarchy .

 IceRPC + Slice Tutorial
 |-- Writing your First Server application 
 |-- Writing your First Client Application
 IceRPC + Protobuf Tutorial
 |-- Writing your First Server application 
 |-- Writing your First Client Application

[pepone]

Let's improve things in a follow-up PR.