Modify Files in ProgrammingAssignment2 Forked Repository

Modified the boilerplate "cachematrix.R" file .Two Functions
"makeCacheMatrix" and "cacheSolve" fleshed out as per the instructions
.The functions replicate the functioning in corresponding functions for
vectors in "cachemean.R" file.
Typos and editorial touches.

Messages tweaked for (hopefully)  better  context display: whether the
retrieved matrix is newly computed or retrieved from the cache.