Refactor parsers into subclasses, fix SOAP envelope, add specs

[keithyoder]

Parser refactor:

• Replace ResponseParser with Base + Autorizacao, Status, Consulta, Inutilizacao subclasses, each with a single #parse method
• Update client.rb to use new parser classes

SOAP fixes:

• Fix SOAPAction in webservices/status.rb (nfcomStatusServicoNF)
• Fix montar_envelope in webservices/base.rb: use soap: prefix instead of soap12:, wrap body with nfcomDadosMsg, run through XmlCleaner
• Fix consulta.rb: use nfcomDadosMsg wrapper, add missing xServ field

DANFE-COM:

• Disable prawn-svg web requests (enable_web_requests: false) in both pdf.svg call sites

Specs:

• Add shared contexts for mocked certificate and default configuration
• Add parser specs for all four subclasses
• Add webservice specs for status and consulta
• Update autorizacao and signature specs to use shared contexts
• Update client_spec to use new parser class names
• Add model specs for Emitente and Destinatario
• Add DanfeCom builder spec with synthetic fixture XML
• Delete response_parser_spec.rb