Implement a way to use the same license key for all plugins on that site

[JurriaanK]

I am looking for a relatively easy way to implement this.
For example: a checkbox, which if marked, saves the license key to a global option when the settings are saved. If that option exists it is used when the license key field of the other plugin is empty. Needs some more thought.

[JurriaanK]

Another idea, add a 'GravityWP' item to the Forms menu. I like how Gravity Perks does this. For now we don't need plugin management. Only site-wide license key.