Merge pull request #670 from gustavofonseca/datamodel-overhaul

Implementação inicial do IssueBaseForm e RegularIssueForm
Implementação inicial do SupplementIssueForm usando IssueBaseForm #674

Issue: #674

- Adiciono clase form para o tipo: SupplementIssueForm descrito em #573.
- Adiciono os tests.
Merge pull request #678 from jfunez/674_datamodel_overhaul_SupplementIssueForm

674 datamodel overhaul supplement issue form