Update WindowsBuild.md
- remove numbers on steps, they get out of sync and auto-numbering headers doesn't work
- correct some header titles
- re-render the tree to be ascii pretty
- split out "one-time setup" from "getting started"
- fix invocation of cmake for toolchain
- fix libdispatch build rules
- convert libdispatch build rules to be copy-paste friendly
- add libdispatch test instructions
