Fix KT-4168 use proper buildscript classpath
Merge remote-tracking branch 'origin/pr/401'

Conflicts:
	libraries/tools/kotlin-gradle-plugin-core/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinPlugin.kt
	libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/KotlinGradlePluginIT.kt
Remove unused resources