Add array storage accounting and reporting

[maherou]

Add tracking of total bytes used in array storage.

[maherou]

Many users have requested information about the total memory used by HPCG. Tracking and reporting the amount of array storage should address this issue.

[maherou]

This feature is complete for now. One big plus from this feature is a sense of the approximate memory usage as a function of the number of equations. The reference version uses about 750*n bytes where n is the number of global equations (or on each MPI process for the local amount of storage). Optimized versions will likely use more memory, but it will still likely be some linear function in n, or approximately so.