grbase: Computes gradient of function
In QuantumClone: Clustering Mutations using High Throughput Sequencing (HTS) Data

Computes gradient of function

1	grbase(fik, adj.factor, centers, Alt, Depth)

`fik`	Evaluation of fik for previous iteration
`adj.factor`	Factor to compute the probability: makes transition between the cellularity of the clone and the frequency observed
`centers`	vector with cellularity of each clone (numeric vector, ordered by samples)
`Alt`	Matrix with number of draws in rows for a mutation/possibility, and samples in columns
`Depth`	Matrix with number of not draws (Depth - Alt) in rows for a mutation/possibility, and samples in columns

fik<-matrix(c(1,0,0,1),nrow = 2)
adj.factor<-matrix(1/2,nrow =2 ,ncol =1)
centers<-c(0.25,0.75)
Alt<-c(125,375)
Depth<-c(1000,1000)
grbase(fik,adj.factor,centers,Alt,Depth)