Add ContactPerson tag in metadata for aggregator (required by Avviso nr. 19 v4)

[SeemoneB]

[lussoluca]

Is this related to https://github.com/italia/spid-php-lib/pull/114 in any way?

[SeemoneB]

Is this related to #114 in any way?

It is similar, but in this PR I managed the tag ContactPerson also for aggregator and aggregated data. One example below

<md:ContactPerson contactType="other" spid:entityType="spid:aggregator">
	<md:Extensions>
		<spid:VATNumber>vatNumber</spid:VATNumber>
		<spid:FiscalCode>fiscalcode</spid:FiscalCode>
		<spid:PublicServicesLightAggregator/>
	</md:Extensions>
	<md:Company>companyName</md:Company>
	<md:emailaddress>companyEmail</md:EmailAddress>
	<md:TelephoneNumber>companyPhone</md:TelephoneNumber>
</md:ContactPerson>
<md:ContactPerson contactType="other" spid:entityType="spid:aggregated">
	<md:Extensions>
		<spid:IPACode>__aggrsint</spid:IPACode>
		<spid:Public/>
	</md:Extensions>
	<md:Company>Organizzazione fittizia per il collaudo</md:Company>
</md:ContactPerson>

As you can see there is the possibility to insert more then one ContactPerson tag and you can define the empty tag like <spid:Public/> or <spid:PublicServicesLightAggregator/>. Required by Avviso nr 19

The next step would be manage the billing information. It can be done easily