Changes and code for validation of SDICA components.

- Change in computeZ.m: the matrix X2 is not sparse, it is better to
use dvd function instead of sods in line 79.

- Change in pcamat.m: In case lastEig > oldDimension, we change the
maxNumOfComp = lastEig. New code in lines 78-81.

- New function permutationTest.m: to compute the t-maps representing
the components extracted with SDICA. The t-maps are obtained in a
non-parametric way using a random permutation test.

- New script: examplePermutationTest.m: Run the permutationTest
function with different parameters and subsets of data.