HIRM assumes noisy_relations are alphabetically after their clean base_relations

[ThomasColthurst]

The HIRM constructor calls add_relation for all the relations in the schema using the default map order, which is alphabetical. But add_relation assumes that base_relations are added before any noisy_relations that use them as their base_relations.

Our one HIRM unit test doesn't uncover this, because it uses relation names of the form R[number], and gives higher numbers to the noisy_relations.

[ThomasColthurst]

Fixed in #132

But we will need to keep this in mind when implementing model 6.