Fix AssemblyResolver
Fix AssemblyResolver

- Assembly key is now in lower case
- Remove useless local
- Add XML doc comments
- Try .exe extension after having tried .dll on all paths
- Don't pass moduleKey to GetModuleSearchPaths()
- Check for empty private path sub dir

ilkerhalil/dnlib,jorik041/dnlib,0xd4d/dnlib,Arthur2e5/dnlib,picrap/dnlib,ZixiangBoy/dnlib,kiootic/dnlib,modulexcite/dnlib,yck1509/dnlib