Update help icon in preference to use png files

[vogella]

The current help icons of the Preference page look bad in the dark theme. I guess they are still gif files.

Would you accept a PR for updating the icons to png files?

[rnveach]

@vogella I can't speak for other admins, but I am willing to look at a PR to update the PNGs. Be warned that you have to support many different flavors of Eclipse as not everyone uses the same version or the same theme.

[romani]

I would use icons from latest icons set of eclipse.

@Calixte , please share your position on this

[Calixte]

Does anyone know if we have to ship our own icons with the plugin, or if we can use the ones from the current theme?

[romani]

I have no idea. Either is fine for me.