General option handling for datatypes

*Title: General option handling for datatypes

Incentive:
Replace the code in shopping functionality which is hardcoded against certain datatypes
to use a more general interface. This will make it much easier to write new datatypes
that supports options.

*Documentation:
A new method is introduced to the eZDatatype interface, it is used to query information about an option.

productOptionInformation(): Returns option information about a given option specified using an option ID
                            The datatype must make sure that the option ID is unique and persisten since
                            the system may ask about this information at a later time.

The method must return the following structure:
- id - The unique ID of the selected option, this must be unique in the attribute and will later on
       be used to recalculate prices.
- name - The name of the option list ( e.g. Color, Size etc.)
- value - The display string of the selected option ( E.g red, green, big, small)
- additional_price - A value which is added to the total product price, 0 or false means no price


datatypes:
Added for eZOption, eZRangeOption and eZMultiOption.

*Testing:

*SVN Revisions:
7505