Add read_model suffix to read model tables

[fabriziosestito]

..for the sake of clarity

[rtorrero]

I started playing a bit with this idea and it turned into a bit of a mess when we reach associations:

When updating e.g. sap_system_read_model.ex, if we don't alter the

has_many :application_instances, ApplicationInstanceReadModel,

line, the tests complain:

** (ArgumentError) schema Trento.SapSystemReadModel does not have association :application_instances_read_model

If we have to change the has_many and also add the suffix there, we lose a bit of readability. After a quick chat with @fabriziosestito we agreed to close this one as WONTFIX for now