[Users] Reorganisation of some of Carpet's internals

[Erik Schnetter]

I have just re-organised some of Carpet's internal operators which
implement the actual copy/restriction/prolongation operators. This
will make it easier to implement new functionality that uses these
operators, such as e.g. periodic boundary conditions within Carpet, or
refluxing. The previous ad-hoc code was causing problems in some
cases, and I hope that this cleaner re-implementation solves these.

The main change is to pass an additional argument "slabinfo" argument
to the operators that can encode additional information, such as is
needed e.g. for periodic symmetries or refluxing. In addition, the
respective ad-hoc "fixes" have been removed.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/