MSI: Add dependancy check for VC++2017

[codebrain]

http://wixtoolset.org/documentation/manual/v3/howtos/redistributables_and_install_checks/install_vcredist.html

Will implement as a simple check and then bail out if it is not installed, with a prompt to install it.

We do have options to bundle the VC++ modules into the installer using the merge modules, but this adds quite a lot of size to the download - we can defer this decision post-alpha.