Move installation.rst to installation/*.rst

- Add index
- Move content to sections
- Rearrange sections

Author: aclark4life

docs/index.rst

@@ -97,7 +97,7 @@ The core image library is designed for fast access to data stored in a few basic
 .. toctree::
    :maxdepth: 2
 
-   installation.rst
+   installation/index.rst
    handbook/index.rst
    reference/index.rst
    porting.rst