Remove unnecessary _setInstaller() function
Move _getFields() into unit test
Return existing promise from show() if mistakenly called twice
Make all status bar indicators inline-block, since that seems to work fine and it makes the spinner work without a special exception
Make all InstallExtensionDialog tests run in the same window so they run fast
Updated install dialog placeholder text to indicate that you can paste in a GitHub repo URL
Install Extension Dialogs run fast now, so moved them into the Unit category.
Merge pull request #3173 from adobe/nj/install-ui-fixes

UI fixes for installer dialog