Display Settings window when app is launched and when clicking dock icon

Description

This change modifies some of the app delegate code to make the app behave in a more standard way. Happy to make changes here if necessary, or just close the PR if you don't feel it's appropriate. Thanks!

Motivation and Context

Normally, when you first open an app and when you click on an app's icon in the dock, the app is activated and brought to the foreground. This doesn't happen by default however if an app only has a Settings window and no other UI.

I have a few little utility apps that fit this, and I've worked up a workaround for the issue. This PR is to bring over the code I use in my apps.

This also has a check to see if the app was launched as a login item. In that case, the main window is not presented, it stays in a hidden state.

Types of changes

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

shapehq / tartelet