doc: Create sphinx project.
doc: Move policies to subdirectory.
doc: Configure for C++.
doc: Split docs.rst into multiple files.
doc: Make docs buildable with sphinx.
doc: Document most new features.
doc: Correct copyright.
doc: Update index.
doc: Typo.
doc: Disable generation of unused indices.
doc: Update documentation on operators.
doc: Add documentation on unnamed classes.
doc: Improve syntax highlighting.