[TYPO3-shop] Mixed currencies in shop

[Franz Holzinger]

Hello Christian,

there is already a currency plugin inside of tt_products, but which did
never work. It would be fine if you could fix the code of this.

The price display functions should be modified also. The
setGlobalMarkerArray should introduce a new marker for the currency,
e.g. ###CURRENCY### and also a ###CURRENCY_DISPLAY### to draw the
currency select box.
But also some currency conversions must be done to show different prices.

- Franz