GlueGen: Add update menchanism

[Croydon]

• Add an UPDATE-mechanism
  * only updating the protobuf file, not completely renewing it

[a-teammate]

This issue is about the bindings between InexorFlex and InexorCore, but possibly also between a InexorCore gameclient and a InexorCore gameserver.

Goal: if you do not change a variable in a drastic way, it will still result in the same network package (with the same ID).
Currently if you add a variable before the one in question, all later variables will signal a different network package (since they have a different ID now).

A pretty cool suggestion is ( (c) @aschaeffer) that the ID could be a hash (i.e. of the variable name and path). That would make it possible, that a modded client could send information only a specifically modded server would use, but any other would ignore.

It is even already needed for not getting ID clashes between different branches of InexorCore when InexorCore <-> InexorCore communication is established.