Rename all documentation files to have .rst extension
|Reported by:||mjtamlyn||Owned by:||nobody|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
All of the docs files are written in reStructuredText, and should probably have the correct extension. Whilst of course one can configure a text editor to use rst syntax highlighting etc, for the new contributor they may not realise to do this.
To be honest, when I first downloaded the docs I was unsure whether the .txt files were actually the docs given that Sphinx docs are written in rst.
Git understands renaming files pretty well, so it should be ok to do this even for people with edits to the file - they should all merge in correctly (with a bit of luck).