Enable easy installation into local Maven repo

To allow easy installation of the built artifacts into the local Maven
repository, this commit applies the Maven plugin to all Gradle
subprojects. As a result, the install task can now be used to perform
the installation
Merge pull request #12 from wilkinsona/maven-plugin

Enable easy installation into local Maven repo
Added afterCompletion to ClientInterceptor

Added the afterCompletion hook to ClientInterceptor, similar to the
existing one in EndpointInterceptor.

Issue: SWS-778