Update endpoints archetypes with new tooling

[frankyn]

• Added Endpoints Frameworks v2.0 support
• Added gradle build support to generated archetype (this is not gradle archetype generation)
• Added support for new AppEngine plugins
• Added comments on how to use Endpoints Frameworks v1.0 support. It's commented unless developer wants to use this framework.
• Updated README.md to reflect changes with new tooling
• Fixed bug where archetype variables weren't replaced when archetype is generated in certain files.
• Updated archetype version to 2.0.0-0 following maven convention.
• Added Jenkins End-2-End testing for hello-endpoints-archetype

[frankyn]

@lesv PTAL

1. Acknowledging comments.
2. Adding a test to verify specific deployed version versus a prior deployment.
3. Updated static pom values

   <groupId>com.example.helloendpoints</groupId>
   <artifactId>helloendpoints</artifactId>

4. Updated Copyrights to be Velocity comments
5. Updated README.md to reflect our conversation.
6. Added e2e test to Jenkins

[lesv]

So the same comments I gave about the sample should apply here, except, of course, the parent pom doesn't appear in the generated code. (Nor do we have copyrights).

[frankyn]

@Les, I modified archetypes to use velocity comments as suggested from a prior meeting. Do you want to remove copyright headers from the archetypes?

[frankyn]

@lesv PTAL