update_mu: Update the Center Values
In SparseDC: Implementation of SparseDC Algorithm

This fucntion updates the center values for each cluster for each iteration of SparseDC. This function runs inside sparse_dc_fun

1	update_mu(C_1, C_2, pdat1, pdat2, ncluster, lambda1, lambda2)

`C_1`	The cluster membership for samples in condition 1
`C_2`	The cluster membership for samples in condition 2
`pdat1`	The centered data from condition 1, columns should be samples (cells) and rows should be features (genes).
`pdat2`	The centered data from condition 2, columns should be samples (cells) and rows should be features (genes). The number of genes should be the same as `pdat1`. as in pdat1.
`ncluster`	The number of clusters present in the data.
`lambda1`	The lambda 1 value to use in the SparseDC function. This value controls the number of marker genes detected for each of the clusters in the final result. This can be calculated using the "lambda1_calculator" function or supplied by the user.
`lambda2`	The lambda 2 value to use in the SparseDC function. This value controls the number of genes that show condition-dependent expression within each cell type. This can be calculated using the "lambda2_calculator" function or supplied by the user.