Updated pom with plugin for JavaDocing

Summary :
[TODO] Javadocing. Adding the maven javadoc plugin in the build for
all the modules.

TestPlan :
Ran $ mvn clean install.
Generates the javadoc in the target of a module.

Reviewers :
Josh Wills

Reported-By :
Josh Wills

SignedOff-By :
Swathi Venkatachala (swatzdev@gmail.com)