Replace libudev backend with sd_device backend

[sonicbhoc]

Closes #36.

Replaces the aged libudev backend with an sd_device backend, and the custom event loop with the general purpose one supplied by libsystemd.

[Jinjinov]

Please revert all formatting changes to Usb.Events.csproj and include only the needed changes.

In Usb.Events.csproj replace -ludev with -lsystemd if needed and test that Usb.Events.csproj works from a clean solution that has no bin or obj folders, no previously built .so files.

[sonicbhoc]

The formatting changes have been reverted. My editor automatically formats files on save, which was fine for the source files but apparently wreaked havoc on the project file.

[sonicbhoc]

Hey, @Jinjinov . It's been about a month. Have you had a chance to look at this? I know you're busy, so there's no rush. I was just asking about progress if any.

[Jinjinov]

My health problems started 3 months ago, so health is now my only priority.

I even stopped working on all my other open source projects.

I don't know when I will start working on any open source project again, but it will be at least a few months - and even then it might not be this project.

[sonicbhoc]

My health problems started 3 months ago, so health is now my only priority.

I even stopped working on all my other open source projects.

I don't know when I will start working on any open source project again, but it will be at least a few months - and even then it might not be this project.

I hate to hear that you're suffering. Get well soon.