Refactored NuGetPacker + Added NugetRestorer
1.Moved common nuget.exe functionality to NuGetResolver
2.Added NuGetRestorer - which adds extensions to restore soluton nuget dependencies
Example where solution is path to sln file:
    Task("Restore")
    	.Does(() =>
    {
        NuGetRestore(solution,
            settings=>settings.SetToolPath("C:/temp/priv/cakeTest/NuGet.exe")
                .WithVerbosityDetailed());
    });
Fixed NuGetRestore naming & added non fluent extension
1.Fixed inconsistent naming of NugetRestoreSettings & NugetRestoreSettingsExtensions
2.Added non fluent settings NuGetRestore extension
Merge pull request #43 from devlead/develop

Refactored NuGetPacker + Added NugetRestorer.