PortalCurrency
----
    >>> from currency.converter.interfaces import IPortalCurrency
    >>> portal_currency = IPortalCurrency(portal)
    >>> portal_currency.portal_currency_code
    'EUR'
    >>> from Products.CMFCore.utils import getToolByName
    >>> properties = getToolByName(portal, 'portal_properties')
    >>> properties.currency_converter_properties.portal_currency = 'USD'
    >>> portal_currency = IPortalCurrency(portal)
    >>> portal_currency.portal_currency_code
    'USD'
    >>> portal_currency.member_currency_code
    'EUR'
    >>> membership = getToolByName(portal, u'portal_membership')
    >>> member = membership.getAuthenticatedMember()
    >>> member.getProperty('currency')
    'EUR'
    >>> member.setMemberProperties({'currency':'JPY'})
    >>> portal_currency = IPortalCurrency(portal)
    >>> portal_currency.member_currency_code
    'JPY'
    >>> portal_currency.selected_currency_code
    'JPY'
    >>> sdm = getToolByName(portal, "session_data_manager")
    >>> session = sdm.getSessionData(create=True)
    >>> session.set('selected_currency_code', 'USD')
    >>> portal_currency = IPortalCurrency(portal)
    >>> portal_currency.selected_currency_code
    'USD'
