specify that icon is only loaded if icons is not defined

[Osmo]

The "icon" value on a lot of prototypes says "Mandatory if icons is not defined."
On some of them, like tips and tricks, it says "Only loaded if icons is not defined.", presumably because it is optional there.
To be more clear, everywhere it is mandatory, it should say "Only loaded, and mandatory if icons is not defined." as icons takes precedence over icon.