Merge Moq.csproj and Moq.NetCore.csproj

The separate .NET Framework 4.5 and .NET Standard 1.3 projects are
merged into a single multi-targeting `.csproj`.

Note that this breaks GitLink, which isn't too much of a problem, as
the `.pdb` files aren't currently included in the Moq NuGet package
anyway, but this will have to be addressed in a later commit.

Moq.NetCore.sln

@@ -19,7 +19,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ClassLibrary2.NetCore", "Un
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Moq.NetCore.Tests", "UnitTests\Moq.NetCore.Tests.csproj", "{193B5DD4-77B8-4B36-8E62-C0E6BD733FAA}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Moq.NetCore", "Source\Moq.NetCore.csproj", "{4BA03097-04CA-4B7C-B618-5AAD1B27B4B5}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Moq", "Source\Moq.csproj", "{4BA03097-04CA-4B7C-B618-5AAD1B27B4B5}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

Moq.nuspec

@@ -187,10 +187,10 @@ Version 1.0
 		</dependencies>
 	</metadata>
 	<files>
-		<file src="Source\bin\$configuration$\Moq.dll" target="lib\net45" />
+		<file src="Source\bin\$configuration$\net45\Moq.dll" target="lib\net45" />
 		<!-- Could not verify that GitLink works, so disabling pdbs for now -->
-		<!--<file src="Source\bin\$configuration$\Moq.pdb" target="lib\net45" />-->
-		<file src="Source\bin\$configuration$\Moq.xml" target="lib\net45" />
+		<!--<file src="Source\bin\$configuration$\net45\Moq.pdb" target="lib\net45" />-->
+		<file src="Source\bin\$configuration$\net45\Moq.xml" target="lib\net45" />
 		<file src="Source\bin\$configuration$\netstandard1.3\Moq.dll" target="lib\netstandard1.3" />
 		<!-- Could not verify that GitLink works, so disabling pdbs for now -->
 		<!--<file src="Source\bin\$configuration$\netstandard1.3\Moq.pdb" target="lib\netstandard1.3" />-->