Fix Directory.Build.props and Directory.Build.targets links in solution items

[vpkopylov]

Turned out I haven't fixed all the issues with Directory.Build.props and Directory.Build.targets in my last PR.

Changes:

1. Renamed Directory.build.props to Directory.Build.props in .sln files
2. Renamed Directory.build.targets to Directory.Build.targets in .sln files
3. Fixed relative paths to Directory.build files in .sln files within Community Modules dir