Fix bugs in paramsel_siglam* and compatibility fixes for test files

[gevangel]

• Bugs in paramsel_siglam and paramsel_siglamho when retraining with opt.paramsel.sigma present: when retraining on the same set, with RBF and asking to re-compute sigma/lambda, even though sigma is not recomputed (due to a check in kernel_rbf), the returned value corresponds to a wrong sigma in opt.kernel.kerrange.
• Compatibility checks in kernel_linear.m, kernel_rbf.m, kernel_chisquared for newprop when opt is passed in. Previously crashed in testall.m.
• Compatibility fixes on test_driver.m and testall.m to run (for gurls upgrade). Now testall.m runs regularily (and in total) as before.
• All files under gurls/test and gurls/demo now run normally.