Added 7zip to automatically create zipped releases
Updated build script to prepare release binaries

Command:
  build.bat /package:<version>

It will create:
 * MSBuild_Platforms_<version>.zip - to be extracted directly into MSBuild
   folder, adding BlackBerry platform for all known Visual Studio versions
 * BBNDK-plugin_<vs-version>_<version>.vsix - set of VSIX packages
   dedicated to each known Visual Studio version