Directory.Build.targets: Fixed project import references so they will work from nested solutions
Directory.Build.targets: Fixed project import references so they will work from nested solutions

NightOwl888/lucenenet,NightOwl888/lucenenet,jeme/lucenenet,apache/lucenenet,apache/lucenenet,NightOwl888/lucenenet,NightOwl888/lucenenet,jeme/lucenenet,jeme/lucenenet,apache/lucenenet,apache/lucenenet,jeme/lucenenet