Delete the clustering project

[LSViana]

Closes #57.

Fixes:

• Remove the unused YDotNet.Server.Clustering and YDotNet.Native project files

[LSViana]

Hi, @SebastianStehle!

I created this PR to drop the projects accidentally added by #55 as you requested in #57. Please, can you review it?

Also, a couple of notes here:

• The Native project being removed here isn't the active one, it's a leftover in the root directory of the repository;
• I added you as a collaborator to the repository, so now you can push & approve changes to this repository
  • I should've done this before but I just noticed you didn't have this permission yet, sorry for the delay.

[LSViana]

I'm going to merge this PR since there's been a period of inactivity here.