Move executables to shoes-core

shoes is just an installation shell. We want a backend to be able to get
everything it needs--primary shoes, backend picker, etc. without
dependneing on that default installation.
README updates based on changes to shoes and shoes-core usage
No, really, don't commit shoes-backend
Fix for running from source on Windows
Windows seemed cranky about shoes --version when unqualified
Use shoes-manual gem

This moves to relying on the shoes-manual gem for providing the manual
support. This includes getting the static files out of shoes-core, and
also moving the manual construction code to shoes-manual.

Conflicts:
	shoes-core/lib/shoes/ui/help.rb
	shoes-core/lib/shoes/ui/manual.rb
Add --manual option to bin/shoes