Catching up ServiceStack.Logging to 3.9.48

Previous NuGet linked to **3.9.44**, which caused build errors in **Mono** when `ServiceStack.*` head version is **3.9.48**.

This pull requests catches up the lagging **3.9.44** NuGet packages to **3.9.48**.

See this problem on StackOverflow:
http://stackoverflow.com/questions/16784739/new-to-c-mono-servicestack-redis-cannot-find-reference/16843995

I think we need some synchronized releases with ***all*** **ServiceStack** packages; otherwise, we start leaving the **Mono** people behind.

### The problem
#### Steps to reproduce the problem

* `ServiceStack.Logging.NLog` is compiled against **3.9.44** on NuGet
* The head version is of `ServiceStack.*` is **3.9.48**.

1. You download NuGet `ServiceStack` **3.9.48**
2. You download NuGet `ServiceStack.Logging.NLog` which is compiled against **3.9.44**

When building using **xbuild** on **Mono** will produce the following:

```
Errors:

/root/tmp/MyProject/Source/MyProject.sln (default targets) ->
(Build target) ->
/root/tmp/MyProject/Source/MyProject.Server/MyProject.Server.csproj (default targets) ->
/usr/lib/mono/4.0/Microsoft.CSharp.targets (CoreCompile target) ->

        Program.cs(47,83): error CS0234: The type or namespace name `NLogger' does not exist in the namespace `ServiceStack.Logging'. Are you missing an assembly reference?
```