Sphinx: make.bat html

[sbrisard]

The make.bat that is automatically generated by sphinx-quickstart has been altered in order to place the generated html files in PROJECT_ROOT/docs (this is required by GitHub pages).

For the time being, the following command is executed

if exist "_build\html\" xcopy /i /s /e _build\html ..\docs

This hack should be made a bit more robust, by

• testing whether the html target was indeed invoked,
• sphinx-build ran successfully.