* Added support for the 'maxdims' and 'maxvars' flags for 'NetCDF'.
* Added the '+mpi' variant and improved dependencies for 'exodusii'.
Improved the 'exodusii' package so that it's less reliant on patches.
* Added better type checking to variant values in the 'netcdf' package.
* Corrected the required CMake version for the 'exodusii' package.
* Fixed the dependencies of the '+mpi' variant of the 'exodusii' package.