Change examples' javadoc to show how to use appassembler

[mziccard]

Right now our example classes contain the following javadoc (example taken from resourcemanager):

Steps needed for running the example:

login using gcloud SDK - gcloud auth login.
compile using maven - mvn compile
run using maven - mvn exec:java -Dexec.mainClass="com.google.gcloud.examples.resourcemanager.ResourceManagerExample" -Dexec.args="[list | [create | delete | get] projectId]"

Once gcloud-java-nio is merged we will move to appassembler hence javadoc should be updated accordingly. /cc @aozarov @jean-philippe-martin

[jean-philippe-martin]

Oh you're right! We could fix those in the gcs-nio branch already.

[mziccard]

This was fixed in #865