New project has broken configuration when git is not in path

[mit-mit]

On Windows, with IDEA CE 2017.1:

1. Use a "clean" IDEA with no plugins installed
2. Install the RC .jar, restart
3. Create new project, incl. enter path to flutter

=> project is created but has broken config:

Project view shows no Dart code:

Launch config has red error cross:

[mit-mit]

Confirmed that Dart SDK is correctly set in settings

[mit-mit]

Hmm, Flutter settings complains that git is not in path. Closing IJ, adding git to path, starting IJ, and creating new project works fine!

But a pretty silent way to fail so badly

[devoncarew]

I'm going to assume that we were able to call flutter create, but that it must have failed with an error. We should do a better job of bubbling that up to the user as part of the project create process.

As part of this, we should probably do more of the creation before we leave the wizard dialog. Currently we do a lot of it in the newly created IntelliJ window.