Updated build script to do an explicit package restore.
Updated build script to do an explicit package restore.

With the [Automatic Package Restore]() functionality introduced by Nuget 2.7 the project nolonger built
from command line. Adding a new target to do an explicit restore on the project fixes the issue.

See: https://stackoverflow.com/questions/22300375/nuget-auto-package-restore-does-not-work-with-msbuild
for more information.

charlesw/tesseract,nguyenq/tesseract