Change namespace to Jackett.Common (#2691)

Really hope I don't break anything with this
Went to have a go at .NET core and it just became too confusing for me with 'Jackett' namespace referring to both Jackett.Common and Jackett

src/CurlSharp/Enums/CurlPipelining.cs

@@ -8,7 +8,7 @@
 // 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 
-namespace CurlSharp
+namespace CurlSharp.Enums
 {
     /* bitmask bits for CURLMOPT_PIPELINING */