Make CGLS restarting optional in python and code it in MATLAB

[AnderBiguri]

When CGLS increases the L2 norm in an iteration, we can instead of just exiting (what MATLAB does now), restart the algorithm. This means calling it again with an initial image of the previous CGLS call output (what python does now).

This is such a common thing for CGLS that it would be worth having it in MATLAB, but also it would be interesting to be able to disable it via kwargs in python.

[AnderBiguri]

related to #19