Check fft algorithm

To reproduce:

• launch a simulation with Stefanescu-Jirsa 3D model and length 1000 ms
• the resulted Raw TS will be of shape (1024*, 3, 76, 3)
• Compute Fourier Analyzer on the resulted TS
• FFT result will have a wrong shape: (512*, 3, 76, 1, 3)
• from the fft algorithm description it should be shape (512*, 3, 76, 3, x*)

Target:

• investigate what is the correct resulting shape
• fix the algorithm (if necessary) in the analyzer
• or fix the visualizers and description for FFT datatype, to match the current resulting shape

Original description:

The Time series data shape was (10, 3, 76, 3) but the resulted computed shape is (5, 3, 76, 1, 3)