So no need for connect window close test here

This removes confusion as to whether you call UAS::requestParameters
(incorrect) or QGCUASParamManager::requestParameterList (correct) from
client code.

This allows use of compile time Object::connect syntax

Simple starting point to view testing

This was leftover from a problem I was having with virtual slots

Allows for UI unit tests to be written:
- Ability to respond to expected message boxes
- Ability to fail test if unexpected message boxes occurs

Allows you to run a single unit test from the command line

- allow unit tests to use QGCApplication
- clear global singletons for each unit test run

Destroyed signal must have been working incorrectly in the past.