E2e testing

[bitdisaster]

An E2E test suite for packaging, installing, updating and uninstalling. The tests are implemented as a separate project under the e2e folder. To run the e2e test do:

cd electron-wix-msi\e2e 
npm i

// launch powershell as admin

cd electron-wix-msi\e2e
npm run test

[coveralls]

Coverage remained the same at 99.552% when pulling 051288a on e2e-testing into 7b4fabb on v3-feature-branch.