v1.3.0: Data encapsulation and access functions (#69)

* Making MPI communicator variables private in parallelComm, and adding access functions

* Making public variables private in the class tioga, and adding access functions

* Private variables and some access functions for the CartGrid class

* More access functions for CartGrid

* Making m_info and m_info_device in CartGrid private

* Access functions for ilo and ihi in CartGrid

* Making the CartGrid member dims and nf private, and adding access functions

* Conversion to private and adding access functions for xlo and dx in CartGrid

* Access functions for ngrids and donor_frac in the CartGrid class

* Making comm_size const in getCartReceptors()

* Making cart_comm_size const in exchangeAMRDonors() and checkComm()