reshaping and enhancement of class makeCacheMatrix

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#NOTE FOR PEER-REVIEWERS: if you are reading this you are looking at a different
# commit with respect to that submitted. This an enhanced versions that fixes some 
# design inefficiences present in the suggested starting script. 
# As a matter of fact, this way the cacheSolve function is no longer needed and all is encapsulated
# within the makeCacheMatrix.
# You should evaluate the other one but any comment or suggestion on this version is welcome :)
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