Fix several bugs in build-razor-winpe.ps1

We were not also installing the en-us cabfiles for language localization.
We do now.

We were also not properly iterating over all the images in install.wim
when injecting drivers.  We do so now.
Merge pull request #29 from VictorLowther/fix-several-build-winpe-bugs

Fix several bugs in build-razor-winpe.ps1