Updating client lib and gradle version.

If you re-deploy an Endpoints app with AppEngine v1.8.4 SDK or later you will
need to update your client libraries in a similar manner because of package
naming changes made. Previously package names were com.google.* but now they
reflect com.appspot.*.

I also updated the gradle to 1.7 and Google Client Libraries to v17.

For reference the following steps were used:

Updated local PATH to include AppEngine 1.8.4.
`cd to appengine-endpoints-helloendpoints-java-maven directory`
Ensured no local changes existed.
`mvn clean install`
`cd target`
`./endpoints.sh get-client-lib -w ./helloendpoints-1.0-SNAPSHOT/ com.google.devrel.samples.helloendpoints.Greetings`
`unzip helloworld/*-java-1.17.0-rc-sources.jar`
`cd helloworld`
`unzip your_app_id_appspot_com-helloworld-v1-20130911203847-java-1.17.0-rc-sources.jar`
`cp -r com ~/appengine-endpoints-helloendpoints-android/HelloEndpointsProject/HelloEndpoints/src/main/java`
`cd ~/appengine-endpoints-helloendpoints-android/HelloEndpointsProject/`
`./gradlew assemble`
The previous step just ensured we can still compile.
`git rm -r HelloEndpoints/src/main/java/com/google/api`
The previous step removed our old libraries.
Ran a sed snippet for each source file to change package names "s/com.google.api.services/com.appspot.your_app_id/"
`./gradlew assemble`
Ensured we can still build
Merge branch 'master' of github.com:GoogleCloudPlatform/appengine-endpoints-helloendpoints-android