add AndroidManifest.xml required AdMob <meta> and <activity>
debug: AdUnit to config.xml and cordova.exec(.., 'showadview')
add gmslib
create.js, copy gmslib
android update project, also run alone for cordovalib (to update gmslib)
CordovaActivity: initAdView(reset), showAdView(show)
PluginManagerService: listen for commands