Add level-0 dense matrix operations
Support for gmpy types is being added to the Matrix module in this PR like the Polys module. In this
PR, manual wrapping of each element of the matrix with a specific domain is required.
But in future work (Upcoming Level 1 of Matrix Module), the code will
figure out the domain of each element itself, as it is done in Polys Module.
Merge pull request #2248 from SaurabhJha/newdense

Newdense