Generate SDK boilerplate code

[afrittoli]

The SDK contains today a lot of boilerplate code which is copied over and over to various events to implement all the getter and setter methods. The initial version of the code was generated through a script which is not up to date now and cannot be used to update existing code either.

The objective of this work is to have repeatable code generation, so that when events schemas change, the code may be regenerated automatically. There are two possible levels of code generation, which can be dealt with in separate issues:

• generate the go types from the schemas
• generate the get/set methods from the go types

[afrittoli]

Consider whether this could be developed to produce code for all SDKs, not only golang

[afrittoli]

Addressed by #43