Supporting xml_root_prefix

[dyron]

Closes #182

[CReimer]

Here's another example of where it's recommended to have standardized prefixes:
https://www-ferd--net-de.translate.goog/aktuelles-veranstaltungen/aktuelles/news/neue-zugferd-version-232-veroeffentlicht?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp
This is one of the two allowed electronic invoice formats mandated by the European Union

xsd2php:
  namespaces:
    'urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100': 'CrossIndustryInvoice'
    'urn:un:unece:uncefact:data:standard:ReusableAggregateBusinessInformationEntity:100': 'ReusableAggregateBusinessInformationEntity'
    'urn:un:unece:uncefact:data:standard:UnqualifiedDataType:100': 'UnqualifiedDataType'
    'urn:un:unece:uncefact:data:standard:QualifiedDataType:100': 'QualifiedDataType'
  destinations_php:
    'CrossIndustryInvoice': ./Model/CrossIndustryInvoice
    'ReusableAggregateBusinessInformationEntity': ./Model/ReusableAggregateBusinessInformationEntity
    'UnqualifiedDataType': ./Model/UnqualifiedDataType
    'QualifiedDataType': ./Model/QualifiedDataType
  destinations_jms:
    'CrossIndustryInvoice': ./Metadata/CrossIndustryInvoice
    'ReusableAggregateBusinessInformationEntity': ./Metadata/ReusableAggregateBusinessInformationEntity
    'UnqualifiedDataType': ./Metadata/UnqualifiedDataType
    'QualifiedDataType': ./Metadata/QualifiedDataType
  naming_strategy: short
  configs_jms:
    xml_cdata: false
  prefixes:
    'urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100':
      'CrossIndustryInvoice\CrossIndustryInvoice': 'rsm'
    'urn:un:unece:uncefact:data:standard:ReusableAggregateBusinessInformationEntity:100':
      'ReusableAggregateBusinessInformationEntity\*': 'ram'
    'urn:un:unece:uncefact:data:standard:UnqualifiedDataType:100':
      'UnqualifiedDataType\UnqualifiedDataType\*': 'qdt'
    'urn:un:unece:uncefact:data:standard:QualifiedDataType:100':
      'QualifiedDataType\QualifiedDataType\*': 'udt'

Unfortunately for it to work properly I would need wildcard support