cleanup warnings

I encountered many errors due to "nested" length (the changes where headers were replaced with `*`). Asterisks don't seem to care how nested they are and work no matter what.

 You can see here an example: http://connortumbleson.com/ci/ci3/libraries/image_lib.html#CI_Image_lib.resize of the sub-headers using asterisks. I don't think it impacts the flow at all.

```
source/libraries/sessions.rst:513: SEVERE: Title level inconsistent:
source/libraries/language.rst:102: SEVERE: Title level inconsistent:
```

Could not fix these two above errors. They are `SEVERE` so the titles are stripped from the HTML, so they do need to be fixed, but since the documentation uses `***` for Class Reference everywhere else it doesn't make sense to use a separate header. I found changing around all the text above (indentation wise) fixed this, but it became a HUGE commit, I'd rather you do it / comment on it.

All other errors are misspellings, poor indentation or bad links.