FxCop compliance for generated NugetVersionAttribute and GitFlowVersionI...

Without the CompilerGenerated Attribute a solution being analyzed with FxCop engine will always fail to build. The following violations will be shown:

````
CA1823	Avoid unused private fields	It appears that field 'GitFlowVersionInformation.SemVer' is never used or is only ever assigned to. Use this field or remove it.	ClassLibrary2	AssemblyInfo.cs	44
CA2243	Attribute string literals should parse correctly	In the constructor of 'NugetVersionAttribute', change the value of argument 'version', which is currently "0.2.0-Unstable0001", to something that can be correctly parsed as 'Version'.	ClassLibrary2	(Global)	
CA1016	Mark assemblies with AssemblyVersionAttribute	Add an AssemblyVersion attribute to 'ClassLibrary2.dll'.	ClassLibrary2	(Global)	
CA2243	Attribute string literals should parse correctly	In the constructor of 'AssemblyInformationalVersionAttribute', change the value of argument 'informationalVersion', which is currently "0.2.0-unstable1 Branch:'develop' Sha:'bb4d4a2d0a69f9dc119310f3dc0051c8d5b019f5", to something that can be correctly parsed as 'Version'.	ClassLibrary2	(Global)	
CA2210	Assemblies should have valid strong names	Sign 'ClassLibrary2.dll' with a strong name key.	ClassLibrary2	(Global)	
CA1813	Avoid unsealed attributes	Seal 'NugetVersionAttribute', if possible.	ClassLibrary2	AssemblyInfo.cs	28
CA1823	Avoid unused private fields	It appears that field 'GitFlowVersionInformation.AssemblyVersion' is never used or is only ever assigned to. Use this field or remove it.	ClassLibrary2	AssemblyInfo.cs	40
CA1810	Initialize reference type static fields inline	Initialize all static fields in 'GitFlowVersionInformation' when those fields are declared and remove the explicit static constructor.	ClassLibrary2	AssemblyInfo.cs	40
CA1823	Avoid unused private fields	It appears that field 'GitFlowVersionInformation.AssemblyFileVersion' is never used or is only ever assigned to. Use this field or remove it.	ClassLibrary2	AssemblyInfo.cs	41
CA1823	Avoid unused private fields	It appears that field 'GitFlowVersionInformation.AssemblyInformationalVersion' is never used or is only ever assigned to. Use this field or remove it.	ClassLibrary2	AssemblyInfo.cs	42
CA1823	Avoid unused private fields	It appears that field 'GitFlowVersionInformation.NugetVersion' is never used or is only ever assigned to. Use this field or remove it.	ClassLibrary2	AssemblyInfo.cs	43
````

With this pull almost all warning will dissapear. One remains though and I have currently no idea how to fix it.

http://msdn.microsoft.com/query/dev12.query?appId=Dev12IDEF1&l=EN-US&k=k(CA2243);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.5)&rd=true

The problem is declarations like the following:

````
[assembly: AssemblyInformationalVersion("0.2.0-unstable1 Branch:'develop' Sha:'bb4d4a2d0a69f9dc119310f3dc0051c8d5b019f5")]
[assembly: NugetVersionAttribute("0.2.0-Unstable0001")]
````
are not valid according to FxCop. One way would be to emit also a suppression like this:
````
[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2243:AttributeStringLiteralsShouldParseCorrectly")]
````
BUT this would remove it globally which might not be intended.