Upgrade Maven Shade plugin to version 1.6

** Bug 
    * [MSHADE-92] - Annotated Method Parameters Not Shaded 
    * [MSHADE-94] - NullPointerException on empty relocation pattern 
(default package) 
    * [MSHADE-104] - Cannot shade aspectj library 
    * [MSHADE-105] - Classes processed by the relocator still have 
references to the original classes in their constant pools 

** Improvement 
    * [MSHADE-111] - minimizeJar should not remove classes 
specifically included by filters 

** New Feature 
    * [MSHADE-91] - Allow using external Shader implementation,