Upgrade to Maven Invoker plugin 3.1.0

** Bug
    * [MINVOKER-191] - "Artifact is not fully assembled" error with maven-invoker-plugin in parallel build
    * [MINVOKER-224] - Unable to set cloneProjectsTo to null

** New Feature
    * [MINVOKER-233] - Call an invoker with a given timeout

** Improvement
    * [MINVOKER-236] - improve display of setup jobs

** Task
    * [MINVOKER-228] - Improve documentation: "Using with other integration test frameworks" page
    * [MINVOKER-237] - Upgrade to JDK 7 minimum.

** Dependency upgrade
    * [MINVOKER-232] - Upgrade parent to 31
    * [MINVOKER-234] - Upgrade maven-shared-utils to 3.2.1
    * [MINVOKER-235] - Upgrade plexus-utils 3.1.0
    * [MINVOKER-238] - Upgrade maven-invoker to 3.0.1