Add COO accessor methods

[KyleVaughn]

Description:This task defines the accessor methods for the COO matrix. These methods are

Tasks: Define the following functions:

std::string getFormat() - get the format of the underlying SpMV format that is being used.
size_t operator() (size_t i, size_t j) : Have operator() to get the data of the matrix coefficients based on the storage map of COO
std::string getFilename() : underlying file for the COO format.
size_t getCoefficient(size_t i, size_t j) : read from the file and get the coefficients.
size_t setCoefficent(size_t i ,size_t j, size_t value) : Set the value of the (i,j) coefficient to the value 'value'
size_t getNumRows() : get number of rows
size_t getNumCols() : gte number of columns
size_t getNumNonZeros(): get number of nonzero entries of the matrix
MatrixState getState() : get state of the matrix

Definition of done: Define the above functions in a proper manner depending on the underlying COO matrix class.

Must include getFormat() and operator()(size_t i, size_t j)

[KyleVaughn]

review by @Aravind-Kulanthaivelu

[Aravind-Kulanthaivelu]

This task is well defined and has mentioned defined functions covers all the required data that needs to be accessed for successful implementation of our program.