Revision 1793

Branch commit.

Removed extractData and archiveData members from DataAbstract and co.
They were removed from Data earlier.

Modified the Data interpolating constructor: Data(Data,FunctionSpace).
If the Data parameter is backed by a DataConstant, the new Data will 
also be constant.
Previously the new Data would have always been expanded.

Note that if the new FunctionSpace would not allow interpolation a 
FunctionSpaceException is thrown (for constant Data) or a 
FinleyAdapterException (for expanded data).