Refactor VuforiaPlugin.java to reduce tech debt
Refactor VuforiaPlugin.java to reduce tech debt

* Refactored `execute()` into multiple helper functions
* Removed some duplication throughout the file
* Tidied up some import statements

Laureckis/cordova-plugin-vuforia-background,mattrayner/cordova-plugin-vuforia,thisisbd/cordova-plugin-vuforia,thisisbd/cordova-plugin-vuforia,Laureckis/cordova-plugin-vuforia-background,happinov/cordova-plugin-vuforia,happinov/cordova-plugin-vuforia,thisisbd/cordova-plugin-vuforia,mattrayner/cordova-plugin-vuforia