mandatory dependency on gradle plugin

[jorgheymans]

We don't use Gradle in our org, so i had the IntelliJ plugin disabled, however it seems that Vaadin Plugin requires it ?

[MarcinVaadin]

It has been used to detect Gradle project properties, I will have a look if still required.

[Artur-]

Can the Gradle dependency be optional? If you have a Gradle project, you likely have the plugin installed and that is also only case when we use it