Only set the graph axis name when it's manually set

[par456]

Describe the new feature

When a graph is created, it often sets the axis name into the axis that is then stored, even if the axis was not manually named. This then causes the name to be copied when the graph is copied and doesn't update when the X or Y axis value is changed. Leading to graphs with incorrectly named axis when you are making a lot at once and working from copies.

Should fix this so that the axis name is only saved if it was actually manually renamed, otherwise it should continue to change based on what the variable it has been set to.

Might need to also clear old graphs that have an axis with the generated name stored so that older files share the behaviour.

[par456]

Wrong PR linked, ignore that.