All methods but 'set_entry' subroutine implemented.

All methods but 'set_entry' subroutine implemented. Planning method to retrieve a specified diagonal.

Currently, the date type matrix multiplication method is consistent with 'matmul' intrinsic on small scale debug test. The matrix multiplication method is consistent with the intrinsic 'matmul' in the the large scale debug in one, two, and three dimensional domains with a single degree of freedom. There is an error with the 'init' subroutine when allocating memory for the 'conodal_entries_field' array (which is only relevant for systems with greater than 1 degree of freedom).