Improve Windows build scripts and documentation

As mentioned in [the Installation guide](https://opencolorio.readthedocs.io/en/latest/quick_start/installation.html), there are two .bat scripts available to help install prerequisites and build OCIO on Windows. These are helpful, however, there are some rough edges with these scripts. For example, some of the instructions are not clear about installing vcpkg. Additionally, instructions should be added for using the Community rather than the Enterprise edition of Visual Studio.

This issue is for someone to take a fresh look at installation on Windows, from the point of view of an inexperienced developer, and make some improvements. Some of the improvements could be to the documentation page and some could be in the .bat scripts themselves.