Remove unused plugin grace-gsp

Closes gh-35

Author: rainboyan

build.gradle

@@ -22,7 +22,6 @@ apply plugin: "eclipse"
 apply plugin: "idea"
 apply plugin: "java-library"
 apply plugin: "org.graceframework.grace-plugin"
-apply plugin: "org.graceframework.grace-gsp"
 apply plugin: "io.github.gradle-nexus.publish-plugin"
 apply plugin: "maven-publish"
 apply plugin: "signing"