implement link_to_remove_fields and link_to_add_fields helper.
implement remove_fields and add_fields functions.
add blocks to display the data_functions in show.html.erb.
modify the software form applied to nested models such as data_functions.
fix the strong parameters to accept the nested model such as data_functions.
change the title bar to link to show the softwares' whole information.
write the styles of data_functions form.