some minor changes and refactoring
some minor changes
some more comments
Some refactor
Merge remote-tracking branch 'origin/IvanChanges'

Conflicts:
	Worksheet 2/calculate_errors.m
	Worksheet 2/derive_G_implicit_euler.m
	Worksheet 2/error_norm.m
	Worksheet 2/explicit_euler.m
	Worksheet 2/implicit_euler.m
	Worksheet 2/newton.m
	Worksheet 2/plot_numerical_solutions.m
	Worksheet 2/solve_with_numerical_method.m
	Worksheet 2/worksheet2.m
	Worksheet 2/write_errors.m
small fix
Minor change
Created some functions for worksheet 3
small change
Merge remote-tracking branch 'origin/master' into Benni