download windows pre-req files using the host OS

[jmartin-tech]

Fix #575 Many pre-req files have moved to require TLS 1.2, to address this downloading these files in the host system will allow this requirement to be meet even when the guest OS being built does not yet support TLS 1.2.

• downloads dotnet and wmf from a provisioner run by the host OS
• updates dotnet to 4.5.2
• update wmf for powershell 5.1
• adjust install process for wmf to run as SYSTEM
• moves boxstarter and Ruby install into the chocolatey_installs path

Further work should be done to validate the download hash and support caching downloads instead of force each build to download again.

This does not remove the need for downloads by chocolatey when preforming those installs.

[jmartin-tech]

Build logs based on this change show that there may still be other issues with the build process that have not yet been accounted for. This should address the failures to build in the Windows 2008 host however some services may still not quite be working as expected.