Fixed bad #ifs for .NET 4.0 vs 4.5
Removed unused methods in Slice, FdbKey and FdbKeyRange, added more test and cleanup

- FdbKey.Ascii/Unicode/Binary are redundant with Slice.FromAscii/Unicode
- Removed FdbKeyRange.All and None, replaced with Empty (default value)
- Validate the arguments better in Slice.Create(...) instead of returning Empty/Nil
- Added a Slice.Random that takes a crypto PRNG
- Removed ToAsci(..,..)/ToUnicode(..,..) that can be replace with  Substring(...).ToAscii()/ToUnicode()
- Some cleanup in Fdb.Errors helpers
- Augmented test coverage on core types
Merge pull request #7 from ajbeamon/master

Update FdbKeySelectorPair.StartsWith to match FdbKeyRange; remove one Snapshot.GetRange overload that doesn't appear to be callable
Merge branch 'master' of github.com:Doxense/foundationdb-dotnet-client
Fixed invalid exception type thrown when calling tr.Cancel()

- return an FdbException with Code 'TransactionCancelled' if tr.Cancel() is called while CommitAsync() is running
- return a TaskCancelledException if the token passed to CommitAsync(..) is cancelled.
"Cancelled" vs "Canceled": The NeverEnding Story

- "Canceled" for public methods, to match the .NET Framework naming (TrySetCanceled / TaskCanceledException / TaskStatus.Canceled ...)
- "Cancelled" everywhere else (comments, messages, ...)
Fixed port of the High Contention Queue

- random benchmark: 10 workers x 100 push/pop: 10.5 sec for simple queue, 5.7 sec for high contention queue
Fixed broken test following changes to FdbKeySelector.StartsWith
Merge branch 'master' of https://github.com/Doxense/foundationdb-dotnet-client

Conflicts:
	FoundationDB.Client/FdbKeyRange.cs