[#60265776] Add vApp/VM power on functionality

* originally in launch.rb, missed from new code (hence BUG)
* added --no_power_on option, otherwise powers on
* refactor in Vapp class to handle getting id without provision step
* bump version to 0.2.0 - technically a new feature
Merge pull request #19 from alphagov/start_vapp

[#60265776] Add vApp/VM power on functionality