Add a meta-description model like SimpleRene

[Nyan11]

The idea is to create a meta-model of Bloc using the simpleRene description language.
And then use this meta-model to automatically generate the Pyramid properties.

For example:

• We can define the concept of "font-size" as a number between 1 and infinity.
• We can defnine the concept of "BlTextElement" as an object link with a "font-size" by the font-size accessor.
• Therefor we can use this information to generate the "font-size" property inside Pyramid for the BlTextElement.

The pros:

• This project is interesting because anyone could add new properties to the meta-model and Pyramid could understand them.
• Therefor a Pyramid developper do not need to know anything about Bloc or Toplo.
• Anything defined by SimpleRene could be editable by Pyramid, not only Bloc or Toplo.
• The definition of Bloc or Toplo could be reuse to create a serializer or to check the precondition/postconditions of the methods.

The cons:

• SimpleRene is "complex", and implementing the different features in Pyramid will be time-consuming.
• We would still need to write all the definitions of Bloc and Toplo using simpleRene, this is also time-consuming.

I dont think anyone except us would need the meta-model of Bloc.
I dont think we should invest the time to do this change.

But if we have the time, this proposition should be done.
It will enable Pyramid to edit anything that has been described with SimpleRene.