Created docs directory (#364)

Copied wiki into docs directory
This allows developers to open pull requests to edit documentation and also use mkdocs to create a styled HTML version

* changed wiki links to relative links

* removed Planned-Features.md

* removed reference to planned features in Home.md

docs/Update.md

@@ -0,0 +1,5 @@
+The detailed documentation is still missing here, but here is an example that might help if you have read about [select statements](Select.md).
+
+```C++
+db(update(tab).set(tab.gamma = false).where(tab.alpha.in(1)));
+```