[maven-release-plugin] prepare release appengine-maven-plugin-1.8.7
[maven-release-plugin] prepare release appengine-maven-plugin-1.8.7

RajMondaz/appengine-maven-plugin,GoogleCloudPlatform/appengine-maven-plugin,tinesoft/appengine-maven-plugin,PeterKnego/appengine-maven-plugin-oath2-config,ludoch/appengine-maven-plugin,renfeng/appengine-maven-plugin,josephburnett/appengine-maven-plugin,rdwallis/appengine-maven-plugin,kuldeep0709/appengine-maven-plugin,ArcBees/appengine-maven-plugin