refactor examples into its own module

[pravsingh]

per conversations at #6 (comment), creating this issue.

aws-encryption-sdk-java\
->    pom.xml   //artifact name for this can be aws-encryption-sdk-java-parent
->    aws-encryption-sdk-java-core
        -> pom.xml, src   //this generates aws-encryption-sdk-java artifact
->    aws-encryption-sdk-java-examples
       -> pom.xml, src  //this generates aws-encryption-sdk-java-examples artifact

Guys put your feedbacks/proposals in the comments section.