Adiciona verificação de presença de allowed_domains em BaseGazetteSpider

[trevineju]

A issue #1314 me fez perceber que estamos deixando passar a verificação da presença desse atributo nas verificações de BaseGazetteSpider. Esta PR incrementa isso na base.

Além disso, os raspadores abaixo serão impactados com o incremento da branch. Precisam ser corrigidos:

• [ ] Please set a value for allowed_domains in al_associacao_municipios
• [ ] Please set a value for allowed_domains in al_maceio
• [ ] Please set a value for allowed_domains in am_associacao_municipios
• [ ] Please set a value for allowed_domains in ba_associacao_municipios
• [ ] Please set a value for allowed_domains in ce_associacao_municipios
• [ ] Please set a value for allowed_domains in ce_sobral
• [ ] Please set a value for allowed_domains in df_brasilia
• [ ] Please set a value for allowed_domains in es_cariacica
• [ ] Please set a value for allowed_domains in go_associacao_municipios
• [ ] Please set a value for allowed_domains in go_federacao_municipios
• [ ] Please set a value for allowed_domains in mg_associacao_municipios
• [ ] Please set a value for allowed_domains in mg_uberaba_2003
• [ ] Please set a value for allowed_domains in ms_associacao_municipios
• [ ] Please set a value for allowed_domains in mt_associacao_municipios
• [ ] Please set a value for allowed_domains in pa_federacao_municipios
• [ ] Please set a value for allowed_domains in pb_federacao_municipios
• [ ] Please set a value for allowed_domains in pb_joao_pessoa
• [ ] Please set a value for allowed_domains in pe_associacao_municipios
• [ ] Please set a value for allowed_domains in pi_associacao_municipios
• [ ] Please set a value for allowed_domains in pr_associacao_municipios
• [ ] Please set a value for allowed_domains in pr_curitiba
• [ ] Please set a value for allowed_domains in rj_associacao_municipios
• [ ] Please set a value for allowed_domains in rn_federacao_municipios
• [ ] Please set a value for allowed_domains in ro_associacao_municipios
• [ ] Please set a value for allowed_domains in rr_associacao_municipios
• [ ] Please set a value for allowed_domains in rs_associacao_municipios
• [ ] Please set a value for allowed_domains in rs_canoas
• [ ] Please set a value for allowed_domains in sc_florianopolis
• [ ] Please set a value for allowed_domains in se_associacao_municipios
• [ ] Please set a value for allowed_domains in sp_associacao_municipios
• [ ] Please set a value for allowed_domains in sp_fernandopolis
• [ ] Please set a value for allowed_domains in sp_macatuba
• [ ] Please set a value for allowed_domains in sp_monte_alto_sigpub