2.5.2

Public release. MvsSln 2.5.2

* NEW: Activating ProjectReferences for existing ProjectDependencies (shallow copy) through new flag.
       Issue #25.
        ```
        ProjectDependenciesXml = 0x0800 | ProjectDependencies | Env,
        ```
            Covers ProjectDependencies (SLN) logic using data from project files (XML).
            Helps eliminate miscellaneous units between VS and msbuild world:
            https://github.com/3F/MvsSln/issues/25#issuecomment-617956253
            Requires Env with loaded projects (LoadMinimalDefaultData or LoadDefaultData).

            A core feature in .NET DllExport Post-processing:
            https://github.com/3F/DllExport/pull/148

* NEW: `ProjectReference` support without obsolete projectguid. Issue #26.

* NEW: IXProject methods:
       ```
       +IXProject.GetFullPath(string relative)
       ```

* FIXED: Fixed possible empty records in SlnParser.SetProjectItemsConfigs.

* FIXED: Fixed `The given key was not present...` when different case for keys in Item.Metadata.

* FIXED: Fixed protected XProject GetProjectGuid() + GetProjectName() when empty property.

* CHANGED: Compatible signature update for `ForEach<T>` extension method:
           ```
           IEnumerable<T> ForEach<T>(this IEnumerable<T> items, Action<T> act)
           ```

* CHANGED: Updated Microsoft.CSharp 4.7.0 (Only for: netstandard2.0 + netcoreapp2.1)

* CHANGED: Updated Microsoft.Build 16.5.0 (Only for: netcoreapp2.1)