A purely virtual class defining a general operator of the form

y = A(x)

Notice that the operator does not have to be linear. Non-linear operator
or operators more complex than just a matrix can inherit from this class.
This allows to write general code for solvers.
Panda_config.h was not actually included in the library. Problem fixed.

Also, changed macro PANDA_HAS_MPI to HAVE_PANDA_MPI
Changed a bit the formatting
Added a constructor for Map which takes only the communicator object and creates an empty map.
Added a macro for C++11 support check
The clone method has to be virtual, otherwise code does not compile.
Improved the definition of the macro regarding c++11: we check the version of gcc to determine the right cxx flag.
Finished to handle the c++11 enabling (hopefully)
Fixed a bunch of bugs in SharedPointer, including missing copy constructor, checks on pointers, pointers reset...
Added the move semantic copy and begin/end iterators. Also, default constructor is now explicit to avoid problems related to implicit cast.
Virtual destructor implementation for Importer was missing (doing nothing)
Detail in MpiComm: the MPI_Comm should be stored as a shared pointer, to avoid problem with the destruction of the MPI_Comm...
Added showMe method and move semantic constructors, in case the passed arrays of elements can be considered as rvalues.
No need to define the macro HAVE_PANDA_CXX11. It's done in the config file. Also, included the utility header for the move semantic stuff.
Starting to work on the CrsGraph class.