solver parsed as 'backslash'

[brossetti]

Pull #2 breaks any example code that calls GaussNewton.m. For instance, E6_HNSP_MLPIR,SSD_affine2D.m breaks at line 65 in GaussNewton.m. There are actually two issues: (1) line 65 of GaussNewton.m has a syntax error and (2) the variable solver is being parsed as the string 'backslash'. Line 65 should be changed from error(1) to error('Error') because error() only accepts strings. A workaround for the second issue is to comment out lines 60-66 in GaussNewton.m. A fix will require further investigation into the parsing of the solver variable.