title: could not find method implementation for arguments in subproject
body: <p>I have a multi-project build that looks like this</p>
  
  <pre><code>talepath-poc-1
      talepath-poc-1-backend
          build.gradle
      talepath-poc-1-ui
          build.gradle
      build.gradle
      settings.gradle
  </code></pre>
  
  <p><code>settings.gradle</code></p>
  
  <pre><code>rootProject.name = 'talepath-poc-1'
  
  include 'talepath-poc-1-backend'
  include 'talepath-poc-1-ui'
  </code></pre>
  
  <p><code>talepath-poc-1</code></p>
  
  <pre><code>plugins {
      id 'java'
  }
  
  group = 'com.lapots.breed'
  
  allprojects {
      group = 'com.lapots.breed'
  }
  
  subprojects {
      version = '1.0-SNAPSHOT'
      repositories {
          jcenter()
      }
  }
  </code></pre>
  
  <p><code>talepath-poc-1-ui</code></p>
  
  <pre><code>plugins {
      id 'org.gretty' version '2.3.1'
      id 'com.devsoap.vaadin-flow' version '1.0.0.RC8'
  }
  
  repositories {
      vaadin.repositories()
  }
  
  dependencies {
      implementation project(":talepath-poc-1-backend")
  
      implementation vaadin.core()
      implementation vaadin.servletApi()
      implementation vaadin.slf4j()
  
      implementation "org.hibernate:hibernate-validator:5.4.1.Final"
  
      implementation "org.vaadin.pekka:checkbox-group-java:1.0.0.alpha1"
      implementation "javax.validation:validation-api:2.0.1.Final"
  }
  
  vaadin {
      productionMode = true
  }
  </code></pre>
  
  <p><code>talepath-poc-1-backend</code></p>
  
  <pre><code>dependencies {
      implementation "javax.validation:validation-api:1.1.0.Final"
      implementation "junit:junit:4.11"
  }
  </code></pre>
  
  <p>But no matter what dependency I put into <code>talepath-poc-1-backend</code> project it always fails with the same exception for any dependency</p>
  
  <pre><code> Could not find method implementation() for arguments [*dependency*] on object of type org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler.
  </code></pre>
  
  <p>While <code>talepath-poc-1-ui</code> works fine. What is the problem?</p>