In backend pipe_control.error_analysis.monte_carlo_create_data() added the argument 'fixed_error' to allow for fixed input of error to the gauss distribution.
Inserted a range of checks, to make sure function behaves as expected.
Task #7882 (https://gna.org/task/?7882): Implement Monte-Carlo simulation, where errors are generated with width of standard deviation or residuals.): Implement Monte-Carlo simulation, where errors are generated with width of standard deviation or residuals.
