new gradle plugins block + fatJar (#560)
new gradle plugins block + fatJar (#560)

* new gradle plugins block + fatJar

* Adding support for the new gradle plugins block
* Using the shadow plugin to create a fatJar for appium java client.

* reverting change

shadow is only on jcenter. So, need to add it to buildscript for satisfying dependency.

* fix repo

SrinivasanTarget/java-client,appium/java-client,saikrishna321/java-client,SrinivasanTarget/java-client,TikhomirovSergey/java-client,TikhomirovSergey/java-client,saikrishna321/java-client,saikrishna321/java-client,SrinivasanTarget/java-client,TikhomirovSergey/java-client,SrinivasanTarget/java-client,appium/java-client,saikrishna321/java-client,TikhomirovSergey/java-client