Windows 10 Universal Platform build compatibility about osvr-unity

[DuFF14]

@demonixis Sounds like a good change. Are you going to open a PR for this repo? How would I be able to test this?
@JeroMiya should probably review the Managed-OSVR changes.

[demonixis]

I can create a pull request last week, I'm just back from vacancy and I've an important update to push quicky.
I saw you're working on two branches (skeleton & android), do you want to merge these branches before my PR?

[DuFF14]

go ahead and create a PR, I don't know if the other PRs will be merged this week or not.

[demonixis]

Great, I prepare the PR today! The second step if you're OK this with could be to centralize all DLLImport into a native or a set of natives file(s). This way we can use an uniq #if !UNITY_WSA define. The same idea could be nice for Managed-OSVR.

I read that the Windows Mixed Reality HMD will be useable from the Unity Editor! I think that we can create a driver for OSVR as well. This could be awesome because for now, those HMD are limited to the Windows Store.

[demonixis]

I just opened #233 with all changes ;)