Introduce `autostart` field on `ServiceInstallCtx`

[jacderida]

Hey Chip,

Here is another PR with a few changes we have found necessary for using the crate in our project. We have a release we need to get out by this Monday, so if it would be possible, a quick merge and publish on this would be greatly appreciated!

• b24eb18 Obtain WinSW location from environment variable

  If WinSW is not at any of the locations specified by the system or user Path variable, check the WINSW_PATH variable for a potential location.

  This is useful because it enables putting the WinSW binary in a location that is not on Path. On Windows, by default there are no locations on Path the user can write to without administrative privileges. Callers of the crate can obtain the WinSW binary and put it in any location they wish, then set WINSW_PATH in the same process, and not have to worry about their users not having the binary in a Path location.

• 17ad9cf Introduce autostart field on ServiceInstallCtx

  BREAKING CHANGE: users who upgrade will need to explicitly add an autostart field into their ServiceInstallCtx definition.

  This controls whether a service should automatically start upon rebooting the OS. It's an option common to all service managers and it's useful for developers to think about whether their services should automatically start up, which I think justifies the breaking change. If the service is resource intensive or uses a lot of bandwidth, some users actually don't want automatic start because it can potentially render their machine unusable.

  It could be that rc.d needs a little bit of additional work here. I am not very familiar with this system.

[chipsenkbeil]

For rc.d, the test is disabled because I had issues with the test runner. Will need to test that manually. Happy to merge for now.

Do you have a crates.io account? I'll add you as a co-owner to the crate so you have the ability to publish. I also sent you an invite to be a collaborator for this repository. At this point, I think you're using it more than I am. :smile:

[jacderida]

Awesome, thank you! I accepted the invitation. My crates.io account is tied to my Github account, so it should be same username, jacderida.

[chipsenkbeil]

jacderida

You should have gotten an invite for crates.io

[jacderida]

Amazing, thanks! I will do a release and publish soon.