Pdb annotation

Changes to the model

• Added a set of Uniprot elements (UniprotRecord class) to Species. Uniprot is mapping between species and structures (species:uniprot == 1:N)
• Added UniprotRecord class which maps uniprot record to a set of PDB records (Structure class)

New annotator which adds PDB annotations

• Creates standard annotations and also adds the mapping to the respective Species objects (Species - 1:N - Uniprot - 1:N - PDB).